Even the delegates to the 1944 Democrat convention couldn’t stomach renominating Henry Wallace as Vice President knowing that Roosevelt was unlikely to serve a full fourth term.
The Catholic who was the Democratic chairmen pushed Truman forward, because he knew Harry was anti-Communist and because Jimmy Byrnes was not acceptable to his fellow Catholics because of his divorce. Catholics and Communists were bedfellows in the Democratic Party, and the Catholic pols had an idea who was to be trusted and who not.