What should you watch for in tonight’s Republican debate?

Never mind what it tells us about Mitt Romney’s frontrunner status — or Tim Pawlenty’s ability to chip away at it. Early debates are hardly make-or-break. Sure, campaigning, including debate performance, can matter in primary election contests (because voters are trying to decide between similar candidates without the benefit of party labels). But a single debate, long before the first voters get involved, isn’t apt to do much to the standing of any of the candidates.

What is more interesting, I think, are the dynamics of the debate. The candidates tonight include frontrunners Mitt Romney and Tim Pawlenty; libertarian Ron Paul; and four implausible nominees who are more-or-less competing with each other for the same niche: Michele Bachmann, Herman Cain, Rick Santorum, and Newt Gingrich.

What will those four try to do to differentiate themselves from the likely nominees and from each other? And what will Romney and Pawlenty do about it?

What I’ll be watching for is whether any of the four successfully finds policy positions that appeals to movement conservatives but is difficult for Romney and Pawlenty to embrace, either because it’s opposed by important interests within the party (such as some anti-immigration measures that businesses don’t like) or because it’s highly unpopular with median voters in the general election. Some of the latter, of course, has already happened with the House budget and Medicare plan. And the severe blowback that Newt encountered after criticizing the Medicare plan is a sign of just how rocky things can get when a 2012 hopeful departs from the party line on an issue that’s viewed as intensely important by the base.

Will there be more of that tonight?