He wouldn't run again. Supposedly he wanted to be the first leader of the United Nations after the war.
Presumably Truman and Dewey still are the nominees, and I bet Truman still wins. It's possible FDR might even step down early to go to the UN and let Truman take over after the war, meaning the situation probably wouldn't be too different except Truman would have FDR's active support behind him which could be an extra asset for him.
I don't think Truman would have been the nominee as sitting vice president. He was not a member of FDR's inner circle and probably wouldn't even seek the presidency himself. Maybe Eisenhower runs four years early and wins handily? Dewey becomes Attorney General in his cabinet then.
Not sure Roosevelt would have resigned around 1946 to become UN General Secretary. No president had ever resigned before at that time.
Ike didn’t really want to run, especially in 1948. So I doubt it. Probably still Dewey for the GOP.
And Truman was chosen as VP in part with the understanding that he very well could assume the presidency during the 1944 term. He was a compromise candidate for the convention/party with FDR’s blessing. Little changes there whether or not FDR resigns early. Yeah, VPs weren’t as powerful or seen as “heir apparents” back then like they are today, but Truman was kind of an exception. And yeah, resigning was unprecedented, but so were four terms. I can see FDR resigning both because of his health and to drive home the point that he really did only run again for extraordinary reasons.
