I disagree that a Dewey victory is implausible, for reasons I explained in an old soc.history.what-if post:
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In 1944 Franklin D. Roosevelt defeated Thomas Dewey in the popular vote by
7.5% (53.4%-45.9%). He got 432 electoral votes to Dewey's 99.
http://en.wikipedia.org/wiki/United_States_presidential_election,_1944
In 2012 Barack Obama defeated Mitt Romney by 3.9% of the popular vote.
(51.1%-47.2%). He got 332 electoral votes to Romney's 203.
http://en.wikipedia.org/wiki/United_States_presidential_election,_2012
So which Republican candidate came closer to winning?
Dewey, of course.
Why? Just think of it this way. We'll say that in 1944, Dewey persuades 2.51%
of the total electorate to switch from FDR to him. (Let's assume that the
switch is even in all states, or at least all fairly close states.) With
Dewey doing 2.51% better and FDR 2.51% worse, Dewey carries every state which
he lost in OTL by less than 5.02%. That means he carries (in addition to the
states he carried in OTL) Michigan (19 electoral votes), New Jersey (16),
Pennsylvania (35), Missouri (15), Illinois (28), Idaho (4), Maryland (8), New
Hampshire (4), Oregon (6), and New York (47). That's 182 additional electoral
votes, so Dewey wins with 281 electoral votes, well over the 266 needed.
Now let's say that in 2012, Romney persuades 2.51% of the total electorate to
switch from Obama to him. (Again, we assume the switch is even, at least in
the close states.) With Romney doing 2.51% better and Obama 2.51% worse,
Romney carries every state which he lost in OTL by less than 5.02%. That
means he carries Florida (29 electoral votes), Ohio (18) and Virginia (13).
So he gets 263 electoral votes--still seven short of the 270 he needs to win.
Therefore, even though Dewey in 1944 did worse than Romney in 2012 in the
popular vote and *much* worse in the electoral vote, he came closer to
winning.
Weird thing, the Electoral College, no?
https://groups.google.com/d/msg/soc.history.what-if/6t-kaf8f11A/cUNTpZ7K4rcJ
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Note that of the states I listed as possible Dewey pick-ups in 1944, all but Oregon, Idaho, and New Hampshire have large African American, labor union, and Catholic votes--none of which would care much for Byrnes. (Walter F. White of the NAACP claimed that African American voters would desert FDR *en masse* if he chose Byrnes.) If Dewey carries Michigan, Pennsylvania, New Jersey, Missouri (which FDR carried by less than three percent even with Truman on the ticket...) Illinois, Maryland, and New York (in addition to the states he won in OTL) he gets 267 electoral votes--one more than he needs to win. Would Byrnes cause FDR to lose that many votes? I doubt it, but it is by no means impossible.