With just hours to go before the caucuses in Iowa start, this is a moment for Rick Santorum to dream big. He’s got all the momentum heading into the final days with his rivals for the social conservative vote all fading fast. Ron Paul’s surge may be slowing as his record gets more scrutiny. Meanwhile, Mitt Romney, the frontrunner and likely nominee, is in a strong position to finish first. But if he does, it will only be because he held onto the same 25 percent or so of the vote he had all along, which may keep him within range of Santorum’s last-minute push. Even a vicious public insult directed at him–such as the attack launched by Alan Colmes on Fox News yesterday that Peter wrote about earlier–has turned out to be a plus for Santorum. It not only garnered him sympathy but allowed the public to see a human side to a candidate who is more of a policy wonk than a glad-hander.

Let’s assume for a moment Santorum’s months of hard work beating the bushes in the backwoods counties of Iowa is about to pay off with an incredible upset victory. The question will then be not so much a post mortem of the losers’ efforts but whether the former Pennsylvania senator has a viable path to the nomination, or if he will be this year’s version of 2008 Iowa victor Mike Huckabee?

The obstacles for Santorum after Iowa have little to do with his message or politics. The conceit behind Santorum’s presidential bid was never farfetched, even when he was at the bottom of the polls. There was always a strong argument to be made that a former senator with impeccable social conservative credentials as well as a strong record on foreign policy would be attractive to Republicans. Indeed, such a profile seems a more likely resume than that of Romney, whose Massachusetts health care albatross should have made his nomination unthinkable had there been a more viable conservative alternative. Santorum’s problems were rooted in his landslide loss for re-election in 2006. Pennsylvanians rejected him because he was seen as a creature of the far right on social issues and out of touch on others. The notion of a man who could be beaten that badly in his own state being elected president seemed absurd, and that prevented Santorum from running anything but a shoestring campaign.

An Iowa victory will solve one part of that problem. Winning the caucus will make people forget about 2006 for a while. But Santorum’s meager resources outside of Iowa provide a more invidious comparison to the way Huckabee fell short after his moment in the winner’s circle four years ago. Santorum will have to raise a lot of money and recruit staff in a host of other primary and caucus states to be competitive elsewhere. Even after an Iowa victory that is easier said than done. There simply isn’t enough time for him to mount an effective challenge in South Carolina later this month, though Iowa could give him a boost there. But there is more than enough time for him to put up a good fight in the Super Tuesday states in March and those that follow.

If the rest of the conservative field bows out by the end of January–leaving Santorum as the leading conservative–then the talk of Romney’s inevitability might cease. Up against a moderate and an extremist like Paul, Santorum would suddenly not seem like a long shot.

Michele Bachmann might, despite signs of her desire to stay in the race, gratify Santorum by dropping out sooner rather than later. But if Rick Perry, who despite his terrible performance so far is holding onto his hopes of turning the tide in southern and western states, stays in along with Newt Gingrich, then the Santorum scenario starts looking less realistic.

Santorum’s general election prospects against Barack Obama are clearly less rosy than those of Romney, because his hard core social conservatism will, as it did in 2006, come back to bite him. But unless the field winnows down quickly for Santorum, then we’ll probably never get to find that out.