Do you think Thomas Dewey will win re-election as US President in 1948?
I would think so. OTL Dewey was a political moderate who had good relations with labor unions while Governor of New York, so assuming his TL-191 counterpart is similar, he should be able to effectively manage any post-war labor unrest and will probably pursue a moderate domestic agenda that will be broadly popular with swing voters (President Dewey might even be the TL-191 president who finally gets social security enacted since congressional Democrats are unlikely to fillibuster a bill from a president of their own party.) There also shouldn't be any major foreign policy crisis in his first term as the Germans want to work with the U.S. to prevent nuclear proliferation, the Japanese are going to be too busy fighting the British and Russians (and probably won't want to risk another war with the U.S. until they have their own nuclear weapons), and the Confederates and Canadians both appear to be too beaten down to cause any major trouble in the short run. Besides which the Socialist brand has been so discredited by the Richmond Agreement that I doubt the public will be ready to seriously consider a Socialist presidential candidate in 1948.
The only real risk to Dewey would be if Morrell decided to run for president, but that seems very unlikely since Morrell doesn't seem to have any interest in political office (and appears to be a Democrat anyway.) I don't think there is any other TL-191 general with enough prestige to be a plausible presidential candidate against Dewey.