No.
Nixon was the only President to resign from office.
President Nixon is known for being the only president in U.S. history to resign from office. He resigned in 1974 following the Watergate scandal, where his involvement in illegal activities, including the cover-up of a break-in at the Democratic National Committee headquarters, was revealed. No other president before or since Nixon has resigned from office.
Richard Nixon is the only president who failed to complete his term for reason other than death. Nixon resigned voluntarily, but quite possibly would have been forced out if he had not resigned.
Richard M. Nixon, who was elected President in 1968 and re-elected in 1972, resigned from office effective at noon on August 9, 1974. His move came amid impeachment proceedings in Congress related to the "Watergate" break-in and other politically motivated crimes. Vice President Gerald Ford became the 38th President, and subsequently pardoned Nixon. However, several of Nixon's aides and other members of his administration were tried and convicted for crimes or the subsequent cover-up. Richard M. Nixon
No. He must resign any other offices before he is sworn in as President. He can run for President while he holds another office.
Richard M. Nixon
The President can not hold any other offices while he is president. (I suppose he could run for some other office and then resign one of them if he is elected to both. This will never happen for several reasons. )
Richard Nixon (January 9, 1913 - April 22, 1994) was the 37th President of the United States, in office from 1969 to 1974. He served as the 36th Vice President of the United States from 1953 to 1961, the only person to be elected twice to both the Presidency and the Vice Presidency. A member of the Republican Party, he was the only President to resign from office because he was involved in a conspiracy to cover-up illegal espionage and sabotage of Democratic Presidential candidate George McGovern's campaign in 1972. He reestablished diplomatic relations with China.
faced impeachment for his part in the Watergate scandal. (apex)
Congress. The Senate tries impeachments while the House of Represenatives actually impeach. Once the Senate convicts a president or other official of impeachment, their removal from office is immediate.
I can only think of one President who didn't finish his term and that was Nixon. The only other President's who didn't finish office were killed in office and the way your question reads you aren't asking about them.
Gerald Ford. Richard Nixon chose Ford as his Vice President after the resignation of Spiro T. Agnew. Ford then became President upon Nixon's resignation. The other vice-presidents who assumed the Presidency were elected as vice-presidents.