In February 2017 Trump’s new national security adviser, Michael Flynn, was forced to resign after press reports disclosed that Flynn had continued to serve in the White House despite a warning from the Justice Department that he was vulnerable to Russian blackmail for having lied to Vice Pres. Mike Pence about the substance of a telephone conversation between Flynn and the Russian ambassador to the United States in December 2016. Flynn’s contacts with the ambassador, both before and after the election, had been monitored by the FBI as part of its routine surveillance of the ambassador’s communications and in connection with a then secret investigation since July 2016 of possible collusion between Russian officials and prominent members of the Trump campaign. That investigation had been triggered by information obtained by Australian authorities, who reported to the FBI in May that George Papadopoulos, a foreign-policy adviser in the Trump campaign, had told an Australian diplomat in London that Russia had “dirt” on Clinton, an apparent reference to the stolen emails that were eventually released by WikiLeaks in July. Speculation in the press regarding the existence of the investigation had been repeatedly dismissed by Trump as “fake news” but was confirmed by Comey in testimony before the House Intelligence Committee in March 2017, during which he also contradicted Trump’s claim that Obama had spied on the Trump campaign by tapping Trump’s telephones. Democratic members of Congress, meanwhile, expressed dismay that Comey had chosen to report the discovery of additional Clinton emails in October 2016 but had waited until after the election to reveal the Russia investigation.

After Comey testified again in May about Russian interference in the election, Trump abruptly fired him, ostensibly on the recommendation of the Justice Department, which in memos solicited by Trump criticized Comey for his public disclosures regarding Clinton’s emails. Trump soon acknowledged that he had intended to fire Comey regardless of the Justice Department’s recommendation and that “this Russia thing” was a factor in his decision. Later that month the press obtained a copy of a memo written by Comey that summarized a conversation between Comey and Trump at a dinner at the White House in January. The memo stated that Trump had asked Comey to pledge “loyalty” to him and that Trump had indirectly requested that Comey drop the FBI’s investigation of Flynn. The memo immediately raised concerns, even among some Republicans, that Trump’s actions might have constituted obstruction of justice. The deputy attorney general, Rod Rosenstein, then announced the appointment of former FBI director Robert Mueller as special counsel to oversee the FBI’s investigation of Russian interference in the election and possible collusion between Russian officials and the Trump campaign, which Rosenstein’s appointment order characterized as “any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump.” Mueller was also authorized to investigate and prosecute any federal crimes arising directly from or committed in the course of the investigation, including obstruction of justice, perjury, destruction of evidence, and witness intimidation.

Comey’s testimony in June before the Senate Intelligence Committee—which, like the House Intelligence Committee, was conducting its own investigation—was broadcast live on television, radio, and the Internet. Many Americans watched from bars and restaurants, which opened early in some parts of the country to provide venues for viewing the much-anticipated event. Comey accused Trump and other administration officials of lying about Comey’s effectiveness as director of the FBI, and he attributed his being fired to Trump’s alleged desire to shut down the Russia investigation. Comey also revealed that, after being fired, he indirectly leaked the memo that recounted his dinner conversation with Trump in the hope of triggering the appointment of a special counsel to continue the Russia investigation.

Early in July 2017 the press reported that in June 2016 senior members of the Trump campaign, including its chair, Paul Manafort, as well as Jared Kushner and Trump’s son Donald, Jr., had met secretly in Trump Tower with a lawyer associated with the Russian government. In response, Donald, Jr., issued a statement in which he claimed that the meeting had primarily concerned adoptions of Russian children by Americans and that he had not known in advance who on the Russian side would be attending. Three days later the press reported the existence of emails predating the meeting in which the British publicist Rob Goldstone (who had helped Trump stage the 2013 Miss Universe contest in Moscow) notified Donald, Jr., that the Russian government possessed incriminating “documents and information” on Clinton and offered to set up a meeting to convey them through a “Russian government attorney.” Attendance at such a meeting was potentially a crime under U.S. campaign finance law, which generally prohibits accepting or soliciting foreign assistance in connection with a U.S. election.

In January 2018 President Trump’s legal team acknowledged in a memo to the Mueller investigation that Trump himself had dictated the false account of the meeting (claiming that it had concerned adoptions), thus contradicting earlier statements by his attorneys and by White House press secretaries. In August 2018 Trump admitted via Twitter that the purpose of the meeting was “to get information on an opponent” but insisted that the encounter was perfectly legal, that no information was forthcoming, and that he did not know about the meeting in advance. For the first time, he also publicly (on Twitter) called upon Attorney General Jeff Sessions to put an end to the Russia investigation by firing Mueller—a power, however, that Sessions did not possess, having recused himself in March 2017 after revelations of his previously undisclosed contacts with the Russian ambassador as a member of the Trump campaign in September 2016.

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In October 2017 the Mueller investigation announced a plea agreement with Papadopoulos in which he admitted to lying to the FBI about his contacts with Russian nationals regarding the theft of emails from the Clinton campaign and pledged to cooperate with the investigation in exchange for its promise not to prosecute him on more serious charges. Later that month the Mueller team also unveiled a 12-count indictment against Manafort and his associate Rick Gates (who himself had been an adviser to the Trump campaign), charging them with money laundering, tax evasion, and bank fraud in connection with Manafort’s consulting and lobbying efforts on behalf of Ukrainian political parties and leaders between 2006 and 2015. As part of a plea agreement with prosecutors, Flynn twice pleaded guilty in federal district court to lying to the FBI—once in December 2017 and again in December 2018. (Flynn’s sentencing was postponed by the district court on several occasions, initially to permit Flynn to cooperate with government investigators, which he did until mid-2019.) In February 2018 additional charges were filed against Manafort and Gates in a superseding indictment, leading Gates to reach a plea agreement; Gates’s testimony at Manafort’s trial in July–August was instrumental in securing the latter’s conviction on eight criminal counts. Facing a separate trial on other felony charges in September, Manafort reached his own plea agreement with the Mueller investigation that month.

Also in February 2018 the Mueller investigation indicted 13 Russian nationals and three Russian organizations on charges of conspiring to defraud the United States by interfering in its political and electoral processes, including the 2016 election. The indictment charged that the individual defendants, working in part through facilities provided by the Internet Research Agency (IRA) in St. Petersburg, used hundreds of fictitious and stolen social media identities to spread “derogatory information” about Clinton and to support Trump. According to the indictment, they also engaged in efforts to discourage minorities from voting, promoted allegations of voter fraud by the Democratic Party, purchased political advertisements on social media, and used false U.S. identities to organize on-the-ground political rallies in several states.

Acting on a referral by the Mueller investigation, in April the FBI raided the home and office of Michael Cohen, Trump’s personal attorney, seizing business records and recordings of telephone conversations between Cohen and his clients, including Trump. According to press reports, Cohen was being investigated on charges of tax evasion, bank fraud, and violations of campaign finance law in connection with his role in making or arranging hush-money payments in 2016 to Stormy Daniels and the model Karen McDougal in fulfillment of nondisclosure agreements concerning their alleged affairs with Trump in 2006–07. In March both women filed lawsuits seeking to have their agreements declared invalid. Cohen eventually pleaded guilty to eight criminal counts in August 2018 in a hearing at which he stated under oath that Trump had directed him to make or arrange payments to Daniels and McDougal. (Following the end of his first presidential term in 2021, Trump himself was indicted on state criminal charges of falsifying business records to conceal the Trump Organization’s reimbursement of Cohen for the hush-money payment to Daniels.)

In July 2018 Mueller indicted 12 Russian military intelligence officers for conspiring to interfere in the 2016 election by stealing thousands of emails and other documents from computer servers of the Democratic Party and the Clinton campaign and publicly releasing them through fictitious social media identities and WikiLeaks. The indictment also charged the officers with breaking into the computer network of at least one state board of elections and stealing data on approximately 500,000 voters. (In a secret May 2017 report, later leaked to the press, the National Security Agency [NSA] determined that a total of 39 state boards of election had been targeted.) The announcement of the indictment prompted Trump to again express doubt that Russia was responsible for the interference, as he had done on several occasions since the beginning of the Russia investigation, and to again assert that the FBI was corrupt and dishonest for not pursuing a criminal investigation of Clinton.

In September 2018 Papadopoulos was sentenced to serve 14 days in a minimum-security federal prison for lying to the FBI, becoming the first Trump campaign official to be jailed in connection with the Russia investigation. Two months later, in November, Mueller informed a trial judge that Manafort had violated his plea agreement by again lying in interviews with investigators and by making false statements before a grand jury. Manafort was eventually sentenced to a combined 7.5 years in prison by two federal courts in March 2019. Later that month he was charged with an additional 16 state felonies by the district attorney for Manhattan. Meanwhile, in November 2018, Cohen pleaded guilty to separate charges of lying to Congress for having told the House and Senate intelligence committees that Trump’s efforts to build a hotel in Moscow had ended in January 2016, when, in fact, they had continued until at least June of that year, by which time Trump had become the presumptive Republican presidential nominee. Cohen was sentenced to three years in prison in December 2018.

Also in November 2018, Trump fired Sessions and appointed as acting attorney general Matthew Whitaker, Sessions’s former chief of staff, who had been an outspoken critic of the Russia investigation before joining the Justice Department. Controversy over whether Whitaker should recuse himself from the investigation was soon overshadowed, however, by Trump’s nomination in December of William Barr as Sessions’s permanent successor. Barr, who had served (1991–93) as attorney general in the George H.W. Bush administration, was known for his extreme view of executive power—one that entailed, among other things, that presidents cannot commit obstruction of justice through the exercise of the discretionary powers granted to them by the Constitution. Notably, Barr relied upon that theory to question the legitimacy of the Mueller investigation in an unsolicited memo that he submitted to the Justice Department in June 2018. The memo, which came to light soon after Barr’s nomination, immediately drew criticism from Democrats, who viewed it as an attempt to curry favor with the Trump administration and as a signal of Barr’s apparent willingness to shut down the Mueller inquiry if Trump so ordered. At his confirmation hearings Barr pledged that he would not interfere in the Russia investigation but refused to say whether he would release Mueller’s final report to the public. He was confirmed by the Republican-controlled Senate in February 2019 in a mostly party-line vote.

Approximately five weeks after his confirmation, Barr informed Congress that Mueller had submitted a final report on the results of his investigation and that there would be no additional indictments. (By that time, Mueller’s team had indicted 34 individuals and three businesses on nearly 200 criminal charges and obtained seven guilty pleas.) Two days later Barr sent to Congress an unusual written summary of the report’s contents, in which he stated that Mueller had not found sufficient evidence to establish a charge of conspiracy regarding the Trump campaign’s interactions with Russia and that Mueller had not made a traditional recommendation about whether Trump should be prosecuted for obstruction of justice. Absent that recommendation, he continued, he and Rosenstein had themselves determined that the evidence presented in Mueller’s report was “not sufficient to establish that the President committed an obstruction-of-justice offense.” Barr’s public release of the summary at about the same time, and its wide coverage in the press, encouraged many Americans to assume that Mueller’s report had found no serious wrongdoing by the president, though others remained skeptical. According to press reports in late April, Mueller had privately written to Barr soon after the summary became public to complain that Barr’s characterization of the report to Congress “did not fully capture the context, nature, and substance of this Office’s work and conclusions” and had created “public confusion about critical aspects of the results of our investigation.”

On April 18, nearly one month after his letter to Congress, Barr released a redacted version of the Mueller report. House Democrats welcomed the release but insisted that Barr make available to them all confidential grand jury materials and the redacted passages related to them. After Barr refused, the House Judiciary Committee sued the Justice Department and obtained a court order in October requiring the release of the grand jury materials. That order was later upheld by a three-judge panel of the Court of Appeals for the District of Columbia Circuit, a decision that the Justice Department appealed to the Supreme Court in July. In late November, after Biden’s victory over Trump in the 2020 presidential election, the Court removed the case from its argument calendar at the request of the Judiciary Committee.

The two volumes of Mueller’s report reflected the dual mandates of his appointment as special counsel: the first detailed the goals and methods of the Russian attack on the 2016 presidential election, and the second outlined several potentially obstructive actions taken by Trump in connection with the FBI’s investigation of Russian interference (begun in July 2016) and the subsequent investigation led by Mueller (begun in May 2017).

Mueller’s office concluded in the first volume that there was insufficient evidence to establish that “members of the Trump campaign conspired or coordinated with the Russian government” despite “numerous links” between the two as detailed in the report. In the second volume, Mueller explained that his office had decided not to recommend charges of obstruction of justice against Trump because Justice Department regulations prohibited the indictment or criminal prosecution of a sitting president and because the office deemed it unfair to accuse Trump of a crime outside the context of a formal trial, where he would have the opportunity to answer the charges against him. Nevertheless, Mueller emphasized in the conclusion of the second volume that

if we had confidence after a thorough investigation of the facts that the President clearly did not commit obstruction of justice, we would so state. Based on the facts and the applicable legal standards, we are unable to reach that judgment. Accordingly, while this report does not conclude that the President committed a crime, it also does not exonerate him.

Although the Mueller report appeared to document numerous instances of impeachable behavior by Trump, Democrats in the House were initially divided over whether a formal impeachment inquiry should be opened. Despite demands for immediate action from several liberal Democrats, the House leadership and most other Democratic members preferred a more cautious approach, arguing that most Americans were opposed to impeachment and that Trump could not be removed from office anyway, because he was certain to be acquitted in the Republican-controlled Senate. The latter view, which House Speaker Nancy Pelosi had advocated even before the release of the Mueller report, remained the prevailing position within the Democratic Party until the late summer of 2019 (see below Ukraine scandal).

In December 2019 the Justice Department’s Office of the Inspector General released a report on its investigation of the FBI’s actions during the early stages of the Russia investigation (then code-named “Crossfire Hurricane”). The report addressed, among other topics, whether the FBI had observed proper procedures in opening Crossfire Hurricane and four individual investigations of members of the Trump campaign (Papadopoulos, Carter Page, Manafort, and Flynn) and whether the FBI had placed any undercover agents within the Trump campaign to gain information about possible links and coordination with the Russian government. Although the report concluded that the investigation had been legitimately opened and that there was no evidence of political bias or of FBI “spying” on the Trump campaign, it also faulted the FBI and the Justice Department for serious errors and omissions and at least one case of apparent criminal wrongdoing in its handling of applications (to the Foreign Intelligence Surveillance Court [FISC]) for warrants to surveil Page, then a Trump campaign adviser.

In an extraordinary decision in May 2020, the Justice Department moved to drop its case against Flynn on the grounds that his statements to the FBI were not “materially” relevant to the bureau’s investigation and that, in any event, the investigation of Flynn itself lacked any legitimate counterintelligence or criminal purpose. Although the district court’s refusal to drop the case was eventually upheld by the Court of Appeals for the District of Columbia Circuit, the case became moot after Trump pardoned Flynn in late November 2020. In the last weeks of his presidency, Trump also granted pardons to Manafort and to Roger Stone, a friend and adviser who had been convicted of lying to Congress, obstruction, and witness tampering in connection with the House Intelligence Committee’s investigation of Russian interference in the 2016 election.

Other investigations

As Mueller’s investigation proceeded, and through the release of his report in March, several House committees—including the Judiciary Committee, the Select Committee on Intelligence, the Ways and Means Committee, the Foreign Affairs Committee, the Committee on Oversight and Reform, and the Financial Services Committee—were conducting their own inquiries into possible tax and financial crimes by Trump, the Trump Organization, the Trump inaugural committee, and the charitable Trump Foundation (dissolved in 2018), evidence of which had arisen from Mueller’s investigation and from congressional testimony by Cohen and other Trump associates. At the same time, the office of the U.S. District Attorney for the Southern District of New York (SDNY) continued its separate inquiry into possible tax fraud and violations of campaign-finance law by Trump in connection with the alleged hush-money payments to Daniels and McDougal (that investigation, however, was abruptly closed without explanation in July 2019). Other federal prosecutors, as well as state and local authorities, were looking into possible lawbreaking by Trump in connection with questionable donations to Trump’s inaugural committee, an alleged offer of a presidential pardon to Cohen, misuse of charitable assets by the Trump Foundation, accusations that Trump inflated the value of his assets in four major Trump Organization projects, apparently illegal tax schemes by the Trump family (see above Early life and business career), and other matters. By the summer of 2019 approximately 30 criminal or civil investigations of Trump and his family or associates were underway.

Since the early months of that year, however, the Trump administration had regularly refused to provide documents or witness testimony requested or subpoenaed by Democratic-led House committees investigating alleged corruption, abuse of power, and obstruction of justice by Trump or the Trump administration. In the wake of the public release in April of the redacted Mueller report, Trump publicly affirmed his administration’s refusal to cooperate with the House investigations, declaring that “we’re fighting all the subpoenas.” He and congressional Republicans frequently insisted that all such inquiries were illegitimate politically motivated attempts to embarrass Trump or to overturn the results of the 2016 election. Although past administrations, including the Richard Nixon administration, had also regularly defied congressional oversight, particularly with claims of executive privilege, none had so broadly rejected, on explicitly partisan grounds, any congressional oversight whatsoever. Some constitutional scholars warned that Trump’s refusal to recognize any legitimate purpose to Congress’s investigations of his administration threatened to undermine the constitutionally established separation of powers between the executive, legislative, and judicial branches of government. Soon after Pelosi announced the beginning of a formal impeachment investigation of Trump in September 2019 (see below Ukraine scandal), the White House counsel, Pat Cipollone, announced in a letter to her and other House leaders that the Trump administration would refuse to cooperate with the inquiry in any way, primarily because it allegedly did not afford Trump the due process guarantees provided to defendants in criminal trials. The House investigation, however, was not a trial.

After Michael Cohen’s testimony to Congress in February 2019 that Trump had regularly inflated or deflated the value of his assets in order to obtain bank loans or to reduce his real estate taxes, respectively, the House Oversight Committee in March requested 10 years of Trump’s financial records from Trump’s accounting firm, Mazars, which responded that it could not legally provide the desired records. The committee’s subsequent subpoena was challenged by Trump in a lawsuit against Mazars and the Oversight Committee but ultimately upheld by a U.S. district court and the Court of Appeals for the District of Columbia Circuit. Responding to an emergency appeal to the Supreme Court by Trump’s attorneys, Chief Justice John Roberts, Jr., indefinitely stayed the subpoena while the Court considered whether to review the judge’s decision. Meanwhile, two other House committees, on Financial Services and Intelligence, issued subpoenas to Deutsche Bank, Trump’s primary lender since the late 1990s, seeking nearly 10 years of tax returns and other financial documents; the Financial Services Committee also subpoenaed the U.S. bank Capital One for similar information. Trump’s lawsuit to prevent the two banks from releasing his financial information was rejected by a district court and, on appeal, by the Court of Appeals for the Second Circuit. In a third case, Trump sued New York state officials (and preemptively the House Ways and Means Committee) to block enforcement of a grand jury subpoena to Mazars for eight years of his state tax returns, arguing that a sitting president is immune from state criminal subpoenas. After a district court dismissed that doctrine as “repugnant to the nation’s governmental structure and constitutional values” and the Second Circuit affirmed, the U.S. Supreme Court agreed in December 2019 to hear all three cases, consolidating the first two as Trump v. Mazars. The Court ultimately declined to invalidate the subpoenas in Mazars but remanded the cases to the lower courts for further consideration of their implications for the separation of powers between Congress and the president. In Trump v. Vance the Court rejected Trump’s assertion of immunity but again remanded the case to permit him to challenge the subpoena on other grounds.