Here are some of the reasons why, all just IMNSHO of course:
1) When push comes to shove, Americans usually vote for incumbents, and the more there is on the line, the more likely they are to vote the incumbent. During wartime, Americans are reluctant to change Presidents.
2) Kerry is simply not taken seriously by the Man In The Street. He is seen as a joke, and the butt of jokes. The overall effect reminds me of what it was like when Dukakis ran.
3) Kerry has no real positions and it shows. His proposals on what to do about Iraq (the ONLY issue in this campaign) are laughable. They seem to consist entirely of "Bring in the UN!"
The Oil-for-Bribes program, murder of our troops by "fellow" UN "peacekeepers", the fact that the UN bugged out of Iraq after one bomb, the hatred Iraqis have for the UN - none of these considerations appear to have made the slightest impression on Mr. Kerry. "Bring in the UN!" and all will be well.
Please. This is the best you can do? It's pathetic. If this is all you have to offer America on November 2nd, you can forget it. Who in their right mind is going to vote for that?
Note I don't say all that just because I'm a rightwing-warblogger-your-epithet-here. I say it because when I talk to folks at the watercooler, or on the street, this is the impression I get, that people see Kerry as a lightweight with no viable policy ideas. "Bring in the UN!" just gets derisive laughter and groans now.
4) I have seen many, many proclamations online from lifelong Democrats like me who have gone Republican because of the war. This is very unusual in and of itself, but couple it with the fact that there doesn't seem to be any appreciable traffic in the other direction. Yeah, it's a tiny data point, but I think it speaks volumes.
5) All the above is just where we are today. The Great Rove-Republican Attack Machine hasn't even really gotten started, and won't start for some time yet. Which would be bad enough for the Dems, given their current numbers, if Karl didn't have any real ammunition. But he does. Kerry's public career has given Karl Rove more ammunition than there is in Saddam's stockpiles.
6) Bush is a master poker player and political campaigner. He hasn't really gotten started yet and won't for some time. Kerry doesn't even know what's going to hit him, is my guess.
7) Senator Kerry's almost record-setting anti-Defense voting in the Senate.
8) Senator Kerry's comments and actions on returning from Vietnam. We saw a taste of that this week.
9) Senator Kerry's addiction to kowtowing to the UN and the Axis of Weasels.
10) Senator Kerry's close association with those who were plotting, however tentatively and feebly, to assassinate US leaders.
11) Senator Kerry's comments during the campaign, where he had to go along with Dean's anti-war rhetoric.
12) The media has pulled out all the stops in trying to influence this election. They're never tried this hard before, not even during Reagan, not even during Vietnam. And it doesn't seem to be working all that well. The polls move a few points at the peak of some PR campaign, and that's it. In their frenzy they don't know when to quit and have gone well too far, alienating the Great Middle. Witness the reactions to the grandstanding of Clarke, and then the 9-11 Commission. Most folks seem to have completely written them off, and turned the page. We don't care about the report anymore, because it's become obvious that it's been prepared by partisan (and compromised, in the case of Gorelick) political hacks.
So, I think we can predict that as Bush's numbers hold up, the media will froth more and more and the whole thing will backfire on them, driving people away from the Dems.
13) The Dems have no strategy, no policy, and no platform. Yeah, that may seem unfair or premature given that they haven't had their convention yet, but I doubt there will be much more substance post-convention. The current "alliance of a bunch of little special interest groups" organization of the Democratic insider base means that the platform will be a combination of vague platitudes and specific bones thrown to the special-interest groups. Indeed, right now the Dems just seem like little kids, gain-saying whatever Bush says. "Are Not! Is Too!"
While folks might be willing to take a chance on such in normal times, during wartime this won't cut it.
14) At the end of the day, when the Undecideds are standing there in the voting booth making up their minds, they're just not going to be able to bring themselves to vote for Kerry. The guy is too much of an obvious joke, and an obvious loser. Not a serious person. Already, even now, Americans don't respect him. Yeah, a lot of people are mad at Bush, but when the time comes they're just not going to be able to bring themselves to actually vote FOR John F. Kerry. They will hold their noses and vote for Bush, or Nader if he's still around.
Hence I conclude that Bush is going to win very big. much bigger than the pundits think right now.