Roosevelt overcame strong opposition from conservative leaders in the Democratic Party and had Wallace nominated for vice president at the 1940 Democratic National Convention. The Roosevelt-Wallace ticket won the 1940 presidential election. At the 1944 Democratic National Convention, conservative party leaders defeated Wallace's bid for renomination, placing Missouri Senator Harry S. Truman on the Democratic ticket instead.

Do you know where there's more specific info about how the DNC (or whatever the equivalent was in those days) Bernie'd him?