In May 1973, the Senate Select Committee on Presidential Campaign Activities, headed by Senator Sam Ervin of North Carolina, began televised proceedings on the rapidly escalating Watergate affair. One week later, Harvard law professor Archibald Cox was sworn in as special Watergate prosecutor. During the Senate hearings, former White House legal counsel John Dean testified that the Watergate break-in had been approved by former Attorney General John Mitchell with the knowledge of White House advisers John Ehrlichman and H.R. Haldeman, and that President Nixon had been aware of the cover-up.
Meanwhile, Watergate prosecutor Cox and his staff began to uncover widespread evidence of political espionage by the Nixon reelection committee, illegal wiretapping of thousands of citizens by the administration, and contributions to the Republican Party in return for political favors.
In July, the existence of what were to be called the Watergate tapes–official recordings of White House conversations between Nixon and his staff–was revealed during the Senate hearings. Cox subpoenaed these tapes, and after three months of delay President Nixon agreed to send summaries of the recordings. Cox rejected the summaries.
In what became known as the Saturday Night Massacre, on October 20, 1973, in an unprecedented show of executive power, Nixon ordered Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus to fire Cox, but both men refused and resigned their posts in protest. The role of attorney general then fell to Solicitor General Robert Bork, who reluctantly complied with Nixon’s request and dismissed Cox. Less than a half hour later, the White House dispatched FBI agents to close off the offices of the Special Prosecutor, Attorney General and Deputy Attorney General.
Cox's successor as special prosecutor, Leon Jaworski, leveled indictments against several high-ranking administration officials, including Mitchell and Dean, who were duly convicted. Meanwhile, on November 14, 1973, U.S. District Judge Gerhard Gesell ruled that Cox's dismissal had been illegal.
Public confidence in the president rapidly waned, and by the end of July 1974 the House Judiciary Committee had adopted three articles of impeachment against President Nixon: obstruction of justice, abuse of presidential powers, and hindrance of the impeachment process.
On July 30, under coercion from the Supreme Court, Nixon finally released the Watergate tapes. On August 5, transcripts of the recordings were released, including a segment in which the president was heard instructing Haldeman to order the FBI to halt the Watergate investigation. Three days later, Nixon announced his resignation.