D. faced impeachment for his part in the Watergate scandal,
Explanation:
Nixon was suspected of tampering with the election through a scandal known as watergate. In this scandal, someone broke into Nixon's opponent's office. Eventually, Nixon was tied to this crime and faced impeachment from congress. Additionally, he also lost the trust of voters. So, instead of being convicted and forced out of the white house, he resigned, being the first and only president to resign in office.
