Why Is McCain Running Right?

It's not a rhetorical question, today I'm really wondering why John McCain is running a "base" campaign. The choice of Sarah Palin, for example, was a base pick, aimed at appealing to the Christian Right and other hard-line domestic-issues conservatives, and she is out there running the line that Obama is "different" (black, liberal) and generally riling up the most xenophobic elements in the party, which makes for exciting rallies in a scary, fascist sort of way, but which is almost guaranteed to turn off independents and centrists. But it's not just Palin. No tax increases for corporations and the very wealthy, "victory" in Iraq, opposition to health care insurance reform: what gives? The issue at the moment isn't whether these conservative positions are wise or otherwise. My question today is, why is McCain seemingly driving his campaign over a cliff?
There are several possible explanations. 1) Maybe the campaign is simply so obtuse that they honestly think that rallying conservatives is the same thing as rallying the country. But that seems unlikely (at least for those of them who are not xenophobes from small-town Alaska). 2) More likely, the reasoning is "last man standing": the Republican cannot win without the conservative base, so make sure the base is OK just in case the Obama campaign hits a rock somehow and McCain gets a chance after all. That is, stay prepared to get lucky. That position makes some sense, but only granting that one has already decided that, barring some political catastrophe for Obama, there's now no use in going after the center. Not "prudent but hopeless," rather "hopeless but prudent." 3) But I have a suspicion that something more personal is going on here. This is John McCain's last hurrah. The cap to his political career is the Republican nomination in 2008. That's in the bag. All that is left is coming in with a respectable showing among conservative voters. So get out there and try to make your performance with conservative voters decent enough so you don't spend your twilight years a political laughing stock. Even that isn't terribly urgent: history will blame the Republican defeat on George W. Bush, not McCain. Go get 'em, Sarah!