One difference is that Thomas Dewey had actually done something in his life before he ran for President. Dewey also didn't accuse FDR of knowing about the attack on Pearl Harbor in advance, unlike Hillary "Bush Knew!" Clinton.
IMHO, Has anyone ever thought to bring up the fact that a leader who just found out his country would be attacked would (1)know that his military forces would be reacting however possible and (2) not rush into an angry response just to look good while making a tragic mistake? 7 minutes to react is about enough time to take a deep breath, make a decision and then formulate what to do. On something of this magnitude that's pretty amazing and I'll be the first to say that's alot less time than I'd be able to make the decisions he made.
I think what many of these commie wannabe scum sucking liberal anarchist piles of wet pig feces (yes Mr. Michael Moore, you're included in that group and a LARGE part of it) who complain about the 7 minutes just want Kerry in office so they can think that they've accomplished something no matter how detrimental it is to the country.
But Roosevelt, or his union allies, did put out campaign material that said a vote for Dewey was a vote for Nazi victory. I've seen the ads myself.