When Harold J. Gibbons resigned as Hoffa's executive assistant in December 1963 after a failed coup against the indicted Teamsters president, Hoffa appointed Fitzsimmons to the office. In 1964, Hoffa was sentenced to an aggregate 13 years in prison for jury tampering, conspiracy, and mail and wire fraud. Fitzsimmons was initially not considered to be politically popular enough to succeed Hoffa. But Fitzsimmons was elected General Vice President of the Teamsters in July 1966, which to many Teamsters leaders signalled Hoffa's intention to make Fitzsimmons his heir-apparent in the event Hoffa was imprisoned. On February 28, 1967, the Teamsters executive board passed a resolution appointing Fitzsimmons "acting president" in the event Hoffa was no longer able to carry out his duties.