9/11 changed everything, imho. I think GW is in a better position than GHW. But see my comment above for the real problem.
My suspicion is that if an incumbent loses, it is a clear mandate - a mandate for change. If a sitting president fails to win reelection, I don't think it matters if he is running against Abraham Lincoln or Elmer Fudd.
Kerry has the charisma of a mountain goat. But a better cantidate from the dims could wreak havoc... say a Hillary.
Ultimately, America is less about what has happened in the past, but far more about dreams of what the future holds. That's the Ace card the dims have always weilded.
We'll see. But a lot of things might happen, the fat lady ain't sang a note yet!
It's not the same because for one thing the third-party candidate who will hurt a main-party candidate is Nader not Perot. Nader's candidacy will hurt Kerry. Perot cost Bush I the election in '92.