Richard Nixon's head was a variant of Richard Nixon from the Futurama Multiverse.
This variant of Nixon's early life paralleled many of the others, including the devastating Watergate scandal that ended his presidency with his resignation.
Some time after his death, Nixon was resurrected through the use of Ron Popeil's Head in a jar technology. Some time after that, he was visited in the Head Museum by Phillip Fry, Turanga Leela, and Bender Rodriguez.
Inspired by this, he ran a successful campaign to become President of Earth.