Rick Santorum had two fairly strong debate performances this weekend. His poll numbers, however, have plateaued in New Hampshire and in South Carolina. It isn’t clear whether his lack of TV ad time or, in the case of New Hampshire voters, his emphasis on social issues (and high-visibility arguments at town halls) is at work. Perhaps it is a combination of these, or perhaps he still is a relative unknown to many voters. But it is not too late to pull it together and make a run at Mitt Romney in the South Carolina Republican primary. Far from it.

First, he needs to get on the air in South Carolina with some punchy TV ads telling voters what he believes and why he is the strongest of the not-Romney candidates. Romney is already on the air, as are the superPACs for the other not-Romney candidates.

Second, he has to forget about Rep. Ron Paul (R-Tex.). Paul is not his problem, and Paul’s libertarian voters are not likely to float his way. The time spent wrestling with him in the debates was not productive. The candidate blocking his climb is Newt Gingrich (who is still polling well in South Carolina). If Gingrich comes out of New Hampshire with increased strength, that’s a problem for Santorum, insofar as each is going for the limited-government, pro-Reagan foreign policy and socially conservative base. Gingrich’s personal problems remain a significant barrier to his advancement among social conservatives, and Santorum should capi­tal­ize on that. He should also be crystal clear about Gingrich’s penchant for falling under the spell of liberals (Nancy Pelosi, Bill Clinton).

Third, today Gary Bauer is endorsing Santorum. This is precisely what he needs — a social-conservative icon and Reagan veteran to give him the stamp of approval and convince other conservatives that they have one serious alternative to beating Romney: Santorum. Bauer is an excellent surrogate and Santorum should use him extensively.

Fourth, he better have a good answer on right-to-work legislation in South Carolina, where the Boeing case made this a top issue. In the Sunday debate he argued: “I signed a pledge that I would support a national right to work . . . . it was mentioned this last night, when I was the senator for Pennsylvania, I didn’t vote for it, because Pennsylvania’s not a right-to-work state, and I didn’t want to vote for a law that would change the law in Pennsylvania.” His campaign gave a far better to Quin Hillyer, explaining that he had a change of heart on national right-to- work legislation:

Spokesman Matt Beynon said the switch was sincere, growing in part from discussions Santorum had with tea-party favorite Sen. Jim DeMint of South Carolina. However the switch came about, Santorum answered all nine questions on a recent survey from the National Right to Work Committee in ways that should thrill any conservative. He pledged to oppose compulsory union dues, support repeal of mandatory union representation for federal workers, oppose “card check” union elections, oppose “project labor agreements” requiring union wages even for non-unionized federal work, and took the RTW position on all five other issues in the questionnaire as well.

Because friend and foe alike agree that Santorum’s word is his bond, there is every reason to trust each of those pledges.

He needs to be clear and convincing on this point. It’s an issue that can hurt him.

And finally, he needs to retain his Iowa-induced sunny demeanor (which frayed a little in the Sunday debate) and not try to win the nomination in a single contest. He needs to do well in South Carolina but doesn’t have to win. He has to stay close to Romney and collect the segment of the electorate that at one time was spread among Gingrich, Texas Gov. Rick Perry and Rep. Michele Bachmann (R-Minn.) To the extent he can come in well ahead of Gingrich and Perry in South Carolina and reasonably close to Romney, he remains viable.

To a certain extent New Hampshire has interrupted Santorum’s momentum. But he’s now on to South Carolina, where he can get it back and reassert himself as a solid, full-spectrum conservative capable of going toe-to-toe with Romney. He remains the most plausible — I would argue, only — candidate to block Romney’s road to the nomination.