I’m not much one for “Great Man” theories of our political history – that is, I think most of the writing on twists and turns in American political history overstates the importance of the sensibilities and psychology of individual politicians and understates social movements, cultural trends, demographic shifts, and so forth – but I’ll readily acknowledge that when it comes to, say, the Republican presidential primary for 2008, there are only so many apparent contenders. And an act of hubris or poor strategery that pulls one out of contention can seriously shift the playing field for everybody else.

That’s why Democrats may come to reconsider their glee over George Allen’s “macaca” muck-up of two months ago if it turns out to have indeed taken Allen out of serious contention for the GOP presidential nomination. Because not long ago, George Allen was well-placed to bear the mantle of “Un-McCain,” a charismatic candidate with the right combination of sterling conservative credentials and cultural compatability (however affected) to excite folks from the GOP base, particularly Christian conservatives, either nonplussed or turned off by a McCain candidacy. The evidence of racial animus on his part could have been just enough to let him take the primary but not the general election.

Now, not so much.

And just as Hillary Clinton’s best chance of taking her party’s nomination is the scenario in which a single charismatic, consenus “Un-Hillary” never quite materializes, for the GOP nod to go to McCain, whose otherwise right-wing record is marred by opposition to global warming, hard money, and torture, and by some carefully chosen symbolic snubs to the base, is the absence of a single viable “Un-McCain.”

Maybe what’s most striking in all this is the lack of a strong McCain alternative to gather in all the GOP activists under one placard. First it was supposed to be Bill Frist. Then he got outplayed by the “Gang of 14” over judicial nominations. And his impressive conversion on the road to Iowa into a religious right zealot was undercut by his betrayal on stem cells.

Rick Santorum, one of the most telegenic elected Republicans out there, from one of the states the party is trying hardest to bring back into its column, is now on track to get kicked out of office by Keystone State voters.

Mike Huckabee has so far failed to make a name for himself for more than losing weight – except with the Club for Growth and the economic right-wingers in its orbit, who hate his guts more than most non-McCain GOPers’.

Mitt Romney, though he pulled off an impressive ground game in the SRLC straw poll six months ago, is still going to have a hard time as the Mormon Governor of Massachusetts exciting the base enough to avert a marriage of convenience to McCain.

Newt Gingrich, like Gary Hart in the lead-up to ’04, seems to have underestimated the staying power of his scandals and overestimated the yearning of the American people for a wonk.

Rudy Giuliani believes in the right to choose.

So it’s not clear who is left to stop the steady flow of strategists, fund-raisers, and activists to John McCain, who is by far the most popular advocate of right-wing politics in the United States. After Macacagate, McCain has at least a passable shot at benefiting from the kind of dynamic that played a key role in elevating Bill Clinton in ’92: the absence of a primary candidate beloved by the party’s base.

And while McCain is beatable, he has the benefit of years of praise not only from starstruck journalists but from short-sighted Democrats who’ve boosted his claims to speak for the center of America.

Meanwhile, you’ve gotta wonder what’s going through the head of Sam Brownback, as staunch a social conservative as you’ll find in the Senate, with no bruising re-election fight in sight, no awkward position in the Republican leadership, and no scandal-ridden press clippings to buck.