On September 8, 1974, a month after being sworn in as president, Gerald Ford signed Proclamation 4311, granting Richard Nixon "a full, free and absolute pardon" for all offenses against the United States which he "has committed or may have committed or taken part in" between January 20, 1969 and August 9, 1974. Nixon had resigned on that second date. No charges had been filed against him.
Ford had not been elected. Not to either office. He had been House minority leader and was appointed vice president in December 1973 under the Twenty-fifth Amendment after Spiro Agnew resigned over a bribery case that predated his time as vice president. He became president on August 9, 1974, and the pardon followed four weeks later.
The wording was the point. By pardoning a category of conduct rather than a named crime, the proclamation covered everything the Watergate special prosecutor and a grand jury had been looking at, including the cover-up, and it made Nixon unavailable as a witness in the trials of his former aides. Twelve of them were indicted or had pleaded guilty around then; John Ehrlichman, H.R. Haldeman and John Mitchell went to prison.
Ford's stated reasoning was that the country could not move on while the former president was being tried for a year. He had, by most accounts, also been told by Nixon's staff that the former president was ill, and he had asked for and received assurances from Alexander Haig that a pardon was within his power.
The cost was immediate. Jerald terHorst resigned the same day. He was Ford's press secretary and a friend of 25 years, and he could not support the pardon. Ford's approval rating dropped by tens of points within weeks. He became the first president to testify before a House subcommittee voluntarily, in October 1974, and answered questions about it directly.
He lost the 1976 election to Jimmy Carter by a narrow margin in the popular vote, and the pardon is usually counted among the causes. It became less disputed over time: in 1999, presenting him with the Presidential Medal of Freedom, President Clinton said the pardon had been in the country's interest. Nixon never faced charges and died in 1994.