There's a recent book on the 1944 campaign, I think it's called Final Victory. Having read that on a plane a year or so ago...
-Dewey was a more polished candidate than Willkie.
-FDR was dying of heart failure and until early in 1944, he had a horrible, incompetent doctor who wasn't treating his heart disease in any way. He was only able to campaign because of his new doctor's treatment.
-FDR may have lost even more ground among civilians, but he won a huge majority of military votes, a pretty big group back then. This was actually a huge issue because the GOP wanted to deprive active duty military of their vote and FDR's campaign really counted on their turnout.
Hard to believe that FDR was only 63 when he died. In addition to his suboptimal medical care, his significant use of tobacco didn't help...
Dewey ran quite strong in the Midwest, and he increased the popular vote total in the Border states (such as Missouri, Kentucky, Oklahoma, and Tennessee). He came quite close in Illinois, Michigan, Pennsylvania, and New Jersey (with far more electoral votes in 1944 than today)--which would have given him around 200 electoral votes.
History hasn't been too kind to Dewey--but he had a good 12 year run at the New York statehouse--running again and winning in 1950 after he unexpectedly lost the 1948 Presidential election.
