Say Rick Santorum manages to pull off the upset in Iowa tonight, beating not only Ron Paul but also Mitt Romney to come in first. Then what? Many will say if Santorum could pull off the impossible once (by winning Iowa), why not a second time (by winning the nomination)?

The trouble with that line of thinking is that Santorum had the luxury of spending months in Iowa running a bare-bones campaign. He won’t have anywhere near as long to work New Hampshire, South Carolina, or Florida. After that, Santorum will need to be able to campaign in multiple states and media markets at once. All with Q4 fundraising totals the candidate himself has said aren’t very good and little time to build up a professional organization.

Being the anti-Romney will confer certain benefits, as many (perhaps most) Republicans would still prefer not to nominate the frontrunner. Santorum could win some Southern primaries simply by showing up. But he didn’t qualify for the ballot in Virginia and has no committed delegates in Tennessee, where Mike Huckabee won in 2008. Both of these are the kinds of states Santorum would need to win to beat Romney.

Santorum will emerge as a giant-killer if he wins the Iowa caucuses. But capitalizing on that win may prove a taller order.

Have at me in the comments.