Almost on cue, the blogosphere is lighting up today with talk about the possibility of a Republican presidential candidate emerging in the coming weeks who will save the GOP from being led into November by a weakened Mitt Romney or, even worse, a guaranteed loser like Newt Gingrich. The latest pundit to pick up on this theme is the New York Times’s Ross Douthat, who writes to defend the honor of The Weekly Standard’s William Kristol, whom he feels has been unfairly maligned for his constant calls for an alternative.

Kristol, whom I also greatly admire, needs no help from Douthat in defending his ideas. But the point is not that, as Douthat puts it, “he’s been right all along” about the need for a better candidate. Of course, a stronger field of presidential wannabes would have better served the Republicans. The problem with Kristol’s thesis is not that the GOP doesn’t need a better candidate, but that it is too late for a potential messiah to win the nomination.

Eric Kleefeld at TPM does a good job outlining the difficulties that would face any Republican who declared his candidacy today even if it was someone as widely admired as Indiana Governor Mitch Daniels, for whom Douthat is particularly pining. The primary calendar is such that the filing deadline has already passed to get on the ballot in most states. So what would have to happen for Daniels or any other such savior is the new candidate would have to miraculously win every caucus state and have a successful write-in campaign in the states where the deadline is passed. Oh, and one other thing is required: Mitt Romney would have to drop out and persuade all of his delegates, supporters and financial contributors to back the messiah.

This is, as Kleefeld rightly puts it, pure “political science fiction.” Moreover, if the Gingrich surge is for real and not just a temporary trend, can Douthat or Kristol really be sure the former speaker can’t beat Daniels or anyone else who would parachute into the race with the unhelpful label as the establishment’s replacement for Romney? If the Republican grass roots is willing to embrace a candidate with doubtful general election prospects like Gingrich simply to teach the insiders a lesson, the chances that anyone thus anointed will take the party back from them are slim and none.

Like the savior scenario, the alternative option proposed by those dreaming of stopping Gingrich via a brokered convention is not impossible; it’s just incredibly unlikely and would require a series of even unlikelier events to occur for it to be even a remote possibility.

All of this brings me back to a point I’ve made a few times in the past when similar suggestions were made, though, to be fair, proposals for a late entry by Daniels, Paul Ryan and Chris Christie were much more realistic back in late August and early September than they are now. Anyone who really wanted to be president and thought they could win has already jumped in (and in a number of cases they have also already jumped out again). The only realistic possibilities for the Republican presidential nomination are named Gingrich or Romney with a long shot chance still belonging to Rick Santorum. That this roster of possibilities dismays most Republicans is understandable. But that’s the reality they face.  If you can’t stand Romney, you can back Gingrich or Santorum. And if you are appalled at the idea of Gingrich, then you’ve got to hope Romney pulls himself together in time for this week’s debates and the Florida primary. The GOP must pick its poison.