Actually, if Wendell Wilkie had won in 1940 he would have approched the war like FDR did. Wilkie was not IIRC an isolationist at all.
From what I understood of Willkie, he was initially thought of as an isolationist, and later claimed to be a non-interventionist. Prior to the '40 election, he charged FDR with being a "warmonger." Eventually, he came around to embrace most of FDR's positions (before he died, he left the Republican Party to found the NY Liberal Party, which was created to supplant the Communist-infested NY American Labor Party). Interesting that despite his relatively youthful age when he ran (48), he would not have lived to see the end of the Presidential term, and his running mate, Sen. Charles McNary, both died in 1944 (McNary in February, Willkie, just 3 weeks before the November elections). It surely would've been a politically tumultous year, as Speaker Sam Rayburn would've become President with a vacancy in both offices (and I have no idea whom the Democrats would've put up in '44, as FDR probably would not have been physically up to mounting a rematch campaign).
http://en.wikipedia.org/wiki/Wendell_Willkie