A former President who has served at least two years each of two terms is ineligible to be either President or Vice President. There are no other disabilities in law. President Taft, after serving as president, went on to be Chief Justice of the Supreme Court. read more
Hence an ex-president could (in theory) run for a seat in the House of Representatives, the Senate, or for any state office such as Governor. John Quincy Adams is the only former president to have served in the House of Representatives after his presidency. Andrew Johnson is the only former president to have served in the Senate after his presidency. read more