Glenn Reynolds explores the universe next door:
Would Kerry have won in 2004 if there had been no 9/11 attacks? Possibly. On the other hand, if there had been no 9/11 attacks, Kerry might never have gotten the nomination—his war record, remember, was supposed to immunize him on national security issues, and that was his biggest attraction to many Democrats.
I'm no Harry Turtledove, but in my alt-history version, I think John Edwards or Howard Dean would have been more likely to have gotten the nomination.
Reynolds isn't a Harry Turtledove—more of a Harry Knowles—but I'd really like to read this alternate history in which the Dean movement takes off without a war to rail against. I suppose Reynolds could be saying the Bush administration was so eager to invade Iraq, it would have done so whether or not we were attacked … but that doesn't sound like him.