Gustaf was spot on. Wisconsin never was all that liberal, with only a few exceptions. It's been a swing state for sometime, and it isn't trending Republican now, as evidenced by the fact that Kerry actually won it by a slightly larger margin than Gore. (Yes, Nader was partially responsible for this, but not wholly.)
I think the difference between 2000 and 2004 was statistically insignificant, and if you take Nader into account, you could argue that the state trended Republican from 2000 to 2004. I haven't done an in-depth analysis, though.
