Harry S. Truman in 1944

[President Johnson]

FDR steps down in 1944 due to his poor health. The Democrats nominate relatively unknown Senator Harry S. Truman of Missouri as a compromise candidate. He picks Senator Alben Barklay as his running-mate and faces the Dewey/Bricker ticket in the general election.

Would Truman have won such an election and how does it affect 1948?

[Bigby]

I believe the main deciding factor will be how Dewey campaigns. If we're talking about 1944 Dewey, then Truman might lose. However, it might end up like OTL 1948 if Dewey acts like 1948 Dewey. Another big factor is the lack of the Democratic split in 1944. Unless the Progressives and Dixiecrats rebel 4 years early, then the Democratic coalition that hurt Truman OTL 1948 won't be an issue here.

[🐒Gods of Prosperity🔱🐲💸]

Truman runs on "Let's Finish the Job" on FDR's successes in the war, and attacking corrupt deals in politics and on Wall Street. Dewey campaigns on the need to prepare for an effective post-War economy, criticizing the Democrats implementation of some New Deal programs.  The result is a very close election for Truman, where a few thousand votes in Idaho, or a half a percentage point in Maryland, could have thrown the election to Dewey.   

Sen. Harry S. Truman (D-MO) / Sen. Alben W. Barkley (D-KY)  49.9  266
Gov. Thomas Dewey (R-NY) / Gov. John Bricker (R-OH) 49.1  265

[President Johnson]

Truman runs on "Let's Finish the Job" on FDR's successes in the war, and attacking corrupt deals in politics and on Wall Street. Dewey campaigns on the need to prepare for an effective post-War economy, criticizing the Democrats implementation of some New Deal programs.  The result is a very close election for Truman, where a few thousand votes in Idaho, or a half a percentage point in Maryland, could have thrown the election to Dewey.   

Sen. Harry S. Truman (D-MO) / Sen. Alben W. Barkley (D-KY)  49.9  266
Gov. Thomas Dewey (R-NY) / Gov. John Bricker (R-OH) 49.1  265

Truman loses NY with a popular FDR backing his campaign? I think NY would be close anyway, as Dewey was from that state too.