Actually, all the Moon landings occurred with Nixon was in office, during his first term.
Former Vice President Richard Nixon of California was
elected President on 5 November 1968, defeating Democratic nominee Vice President Hubert Humphrey of Minnesota and former (and later future) Alabama Governor George Wallace of the American Independent Party. He
assumed office on 20 January 1969.
Apollo 11's Eagle module landed on the Moon six months later, on 20 July 1969.
Apollo 12 was launched on 14 November 1969 and landed on the Moon on 19 November.
Apollo 13 launched on 11 April 1970 and of course never landed.
Apollo 14 was launched on 31 January 1971 and landed on the Moon on 5 February.
Apollo 15 was launched on 26 July 1971 and landed on the Moon on 30 July.
Apollo 16 was launched on 16 April 1972 and landed on the Moon on 21 April. Nixon
won re-election on 7 November 1972, defeating U.S. Senator George McGovern of South Dakota.
Apollo 17, the last manned mission to the Moon so far, was launched on the subsequent 7 December and landed on 11 December.
Nixon began his second term on 20 January 1973. He
resigned from office effective 12:00 PM Eastern Time on 9 August 1974, succeeded by Vice President Gerald Ford of Michigan, as a result of the
Watergate scandal.
Since
Doctor Who is a British show, I should probably mention that the U.K. Prime Ministers throughout this timeframe were
Harold Wilson of the Labour Party, who held office from 16 October 1964 to 19 June 1970, and was therefore in office during the first Moon landing and in office during Apollo 12 and Apollo 13, and
Sir Edward Heath of the Conservative Party, who held office from 19 June 1970 to 4 March 1974, serving during the rest of the Apollo missions.
This has been your vaguely useless historical trivia for the day.