Ramesh Ponnuru has, what I think, is a rather fair and balanced look at next year’s election. It will not be a landslide, but it will not be a Bush loss either.
If Bush finds himself sitting comfortably next year (which I don’t expect), he will campaign for House and Senate candidates. That may make a difference in two or three close races. Not much more than that is possible, especially in the House, where most seats are not competitive. A Dean candidacy is unlikely, in short, to result in substantial Democratic losses.