While everyone's looking at Bush's approval ratings, I find it more interesting to look at his disapproval ratings. I think politicians are not elected these days so much as others are defeated. The latest Newsweek poll has Bush at 50% approval which is not great but not fatal. At this point in their respective first terms, Carter had a 52% approval rating and lost badly, while Clinton had a 47% approval rate and won easily.
If I were Karl Rove, the only part of that poll that would worry me is where 47% "strongly" want to see Bush defeated and I'd want to know how strongly. I get the feeling that what will be different about this election from the others I've lived through is that we will see Democrats become more emotional and fervent than usual. In the 2000 election, I never felt that one single person I spoke with or even heard on the news was that passionate to see Al Gore in the White House. I didn't think the other side cared any more about George W. Bush, but they did care about electing a Republican, if only to end The Clinton Era. In fact, the only real fervor I sensed in that whole contest came from those who wanted to repudiate Bill Clinton.
Clinton's disapproval ratings were no higher than most presidents'. At this point in his first term, it was around 40%. Still, based on nothing more than my own reading of the news and chatting with friends, I got the feeling that the 40% who disapproved of him really, really disapproved of him. Reagan, at various points in his presidency, had a pretty high disapproval rating but the folks who comprised it never seemed to feel that the future of mankind depended on the defeat of Reaganism. Similarly, I never felt Clinton supporters hated Bob Dole or the last George Bush as much as their supporters hated Bill and Hillary. (And in '88, as in 2000, I didn't think anyone was particularly passionate for Dukakis or that Bush, but the latter had people on his side who were adamant about not seeing The Reagan Years end. One might argue that neither Bush got elected on his own positives; that the first coasted on good feelings about Reagan and the second on bad feelings about Clinton.)
As I look over the Democratic contenders, I don't see anyone who looks like they can arouse any significant amount of passion in a positive sense. If it's Kerry-Edwards or Dean-Clark or whatever, most people who fight for them will merely be passionate to defeat Bush-Cheney. Given the way a lot of Democrats (and even some Independents and fringe Republicans) are coming to view Bush not just as a poor president but as someone who's genuinely destroying America, that may be enough.