Challenge: All Post WWII Presidential Elections Flipped

How can we reverse the outcome of every American election since WWII, with the opposite party and candidate taking the Presidency? In order to preserve some logic I have had incumbent President's keep office rather than being constantly replaced by other members of their own party after a single term.

This would make the Presidential victors:
1948: Dewey
1952: Stevenson
1956: Stevenson
1960: Nixon
1964: Nixon
1968: Humphrey
1972: Humphrey
1976: Ford
1980: Carter
1984: Carter
1988: Dukakis
1992: Bush
1996: Bush
2000: Gore
2004: Gore
2008: McCain
With the 2012 featuring Incumbent John McCain facing off against challenger Barack Obama.

Anybody care to take a stab at it?
 
A Dewey win alone makes all of that plausible except Ford '76. He can be a simple compromise candidate.
 
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