Personality wins elections; ideology doesn't. Some times, ideology can be used to frame a person's personality (eg, making Dukakis seem unamerican). Given that we have an incumbent, the election is Bush's to lose. But if we have a poor economy and continued problems in Iraq, anybody who has a good campaign can win. This is a big if.
You're right about that. It doesn't really matter what a candidate believes, it's what the voters think the candidates believe. In 1992 whether Bill Clinton actually ran as a moderate or a liberal, he was viewed by the American people as a moderate. Barry Goldwater wasn't any more conservative than Ronald Reagan, yet Goldwater lost in a landslide to LBJ and Reagan won two landslides against Carter and then Mondale. The only reason for Goldwater's loss and Reagan's win was that one was viewed as a radical and the other as a reasonable, if conservative, politician.
In 2004 Dean will not be viewed by the American people as a moderate because of his lefty stances on social issues. Unlike Clinton, Dean will not have a Southern twang to hide behind. There's nothing remotely charming about Dean, unlike Clinton. And Dean won't be facing a politically clueless incumbent like Bush 41.