Why was Richard Nixon the only U.S. president forced to resign?

Richard Nixon was the only president forced to resign because he faced serious accusations of criminal misconduct committed in the Oval Office. These allegations were severe enough that they would have led to his impeachment and removal from office had he not resigned, and potentially could have resulted in federal prosecution and conviction afterward. A month after Nixon's resignation, his vice president who became president, Gerald Ford, issued a pardon for Nixon, protecting him from potential criminal prosecution for actions committed during his presidency. This unique sequence of events—resignation under the threat of impeachment followed by a presidential pardon—marks Nixon's unprecedented position in American presidential history.