It's rather ironic, but Wallace, whom FDR had to force on the party for VP in 1940, was the rank-and-file's favorite for VP in 1944. He actually led on the first ballot for VP.The easiest scenario I imagine however is one that I in years past proposed for 1948, or at least the premise is similar, the primary difference being that Roosevelt dies in say February of 1944 rather then April of 1945. Henry Wallace becomes President, and not being well-versed in his views on the war at the time I'll just assume that the war has gone on as it did. He'd probably seek the Democratic nomination for a term in his own right, and while there would be some manner of sympathy support I think that would be canceled out by the kind of opposition Wallace would face in being nominated for President, which would be far stronger even then the nomination he faced for Vice-President.
The opposition to Wallace in 1944 was behind the scenes, from a group of powerful insiders who thought he would be a dangerous drag on the ticket.
Unlikely, IMO. Wallace was the front-runner for VP in OTL, despite the opposition of party honchos and FDR's non-endorsement.From here it could go one of two ways:
The ABW forces manage to coalesce around a single candidate and win them the nomination. There is an uproar within the Party base that supports Wallace, some of the delegates walk, and efforts are made to the extent that "Wallace for President" tickets are being put onto State ballots. It could go either way, but in this case Wallace decides not to emulate Eugene McCarthy and opts to run Third Party.
ITTL, he is President, and therefore in a much stronger position. There may be a bit of a floor fight, but Wallace should get the nomination. Who, after all, would the insiders line up behind? Jimmy Byrnes, the "assistant President", would be the likeliest candidate, but he was opposed by several key non-Southerners.
And there will be reluctance to oppose the sitting President openly because of the public impression given. He is President because the Democrats nominated and elected him Vice President. If the party repudiates him after such a short time in office, what does that say about their judgement?
Wallace IMO could get the nomination without "convincing" any party honchos. They (some anyway) would simply decide it was not worth fighting a sitting President.Wallace manages to convince a handful of the Party bosses to support him, enough that he wins a majority. There is a strong chance that the a sizable portion of the Southern delegates walk, especially as he was not particularly shy when it came to embracing the advancement of Civil Rights or working integrated crowds, and that in and of itself throws the support of that entire region into question.
And if Southerners openly oppose Wallace over civil rights, it would be very embarrassing for non-Southerners to join them.
In any case, I can't see the civil rights issue becoming that "hot" in the few months between FDR's death and the convention; not with the war still center stage.
In either case Thomas Dewey would be in a particularly strong position to win the election. I'll expand on this more later when I have the time.
I don't see an outright Dixiecrat bolt as in OTL 1948. Wallace is unlikely to do anything drastic enough for that in the short period before the convention. Certainly not desegregate the armed forces - the service chiefs would all vehemently oppose any such disruptive measure in the middle of a war. Especially Marshall, a VMI graduate.
However, Dewey would have a very powerful card to play in the "Dear Guru" letters, which Wallace wrote to the Russian mystic Nicholas Roerich in the 1930s. The letters expressed Wallace's complete belief in Roerich's very peculiar creed, and as Sec of Agriculture, Wallace had sent Roerich (who was something of a scientist and artist) on a botanical expedition to Manchuria. By 1940, Wallace had broken with Roerich, but Republicans had the letters. That year, the Democrats neutralized the letters by threatening to reveal Wendell Willkie's adultery with Irita Van Doren. That wouldn't work in 1944...
So Dewey wins. The next question is what would Wallace do in the lame-duck period (until 20 Jan 1945)? Would he cooperate with Dewey to insure unity of authority, or try to entrench his own policies as much as possible?
Then comes the Yalta Conference. (Only two weeks after the inauguration; might it be delayed to give Dewey a better grip on his new office?)
FDR went to Yalta a sick man, and desperate to win Stalin's cooperation. Dewey would be healthy, and IMO far more skeptical about Stalin. One question is how Dewey and Churchill would get on. FDR liked Churchill, but by 1945, he had come to regard Britain and Churchill as a second-tier player. Dewey IMO would be more respectful of Churchill, being younger and a novice in international affairs.