The head of the Teamsters had been serving a 15-year prison sentence for jury tampering and fraud when President Richard Nixon pardoned him on Dec. 23, 1971. Nixon had one condition, however: Hoffa should "not engage in direct or indirect management of any labor organization" until at least March 1980. Hoffa agreed and supported Nixon's re-election bid in 1972. It is believed that Hoffa was trying to reassert his power over the Teamsters, defying Nixon's requirement, when he disappeared in 1975.