If you go here, here, here, here, here, and here, you can pretty much cover the landscape of arguments for why the polls simply can't be trusted this year.I'm not in the group that says McCain is secretly winning and the polls are a gigantic false-flag psy-ops program designed to discourage GOP turnout. We know, after all, that whatever the biases of various people and institutions involved, the final polls in 2004, properly understood, were highly accurate, and the 2006 polls were mostly so as well (2002, less so). Neither am I in the group that attributes potential poll inaccuracy entirely to Obama's race - while that may well be a factor, I think there are fair arguments that run deeper to polling methodology, and I also think Obama's inexperience, the absence of a candidate from the incumbent administration, the massive new-voter operation by the Obama camp, the Palin wildcard (this has to be the first time ever that a VP pick drew nearly the same convention speech audience as the POTUS nominees and the VP debate outdrew the POTUS debates, and now she's delivered the biggest ratings for SNL in 14 years) and the sudden, late external shock of the credit crisis are all reasons why public sentiment may be more volatile and harder to get a fix on than usual.
Polls are not votes. They are evidence. The likely answer from the evidence we have remains that McCain is losing and likely to lose; I'm not going to cocoon myself or anyone else from that (there's a reason why candidates who say "the only poll that matters is the one on Election Day" usually end Election Day with a concession speech). But there is more than enough uncertainty out there that I endorse wholeheartedly the view that the last thing Republicans and other McCain supporters should do is get discouraged and throw in the towel before every stop is pulled out to win this thing. You gotta be in it to win it.
UPDATE: Geraghty notes here and here the panicked frenzy of attacks he gets from the Left whenever he suggests that some polls are showing a closer race than the conventional wisdom (or the bulk of polls, for that matter). I chalk this up partly to the Online Left's longstanding view that the winner of any argument is the person who can demonstrate the greatest degree of anger, but it's certainly a curious phenomenon coming from people who would seem to have every reason to be confident and no particular reason to take time from their day getting angry at a conservative pundit for showing a glimmer of optimism. Unless you do buy into the view that such people really are banking very heavily on a demoralized opposition.
SECOND UPDATE: It appears that the AP poll showing Obama up only by one has a 4-point advantage for the Democrats in the party-ID breakdown. For anybody who has followed the polls this year, that's the single biggest question: when you factor in GOTV and whether the likely-voter screens and all have or have not accurately predicted who will vote, will the party ID numbers look like 2006, when a terrible climate for Republicans still produced just a 3-point advantage in party ID for Democrats in the exit polls? Or will it be more like a double-digit advantage in party ID, figures we have not seen since the 1970s? Note that the Geraghty posts I linked to up top show very few examples of dramatic changes in party ID year to year. Even in Jay Cost's chart of registered voter ID, the biggest swings are about 7 or 8 points in some years, 1984 and 1994 for the GOP and 1996 for the Democrats. It may well be that 2008 really will show a historic realignment away from the position the GOP held in 2006 (which was already awful, the worst Republican year in a decade), but just bear in mind that it has to be for the bulk of this year's polls to be accurate.