During Franklin D. Roosevelt's (FDR) terms as president, there were three different vice presidents, John "Cactus Jack" Garner, served for two terms from 1933-1941. During FDR's second term, he and Garner clashed over several issues; Garner in turn decided to challenge FDR for the democratic nomination in the 1940 election and lost. The second vice president was Henry Wallace who served during Roosevelt's third term.

Friction that developed between Wallace and other members of the cabinet and his liberal stance soured his chances of nomination for the 1944 election. Leading to the surprise victory of Harry Truman, a relatively unknown senator from Missouri to win the nomination and became the third vice president for Franklin Roosevelt. Truman's term as vice president only lasted a few months, Franklin Roosevelt died in April 1945, with Harry Truman succeeding him as president.

More Info: en.wikipedia.org