We talked last night about the sought after results of the Des Moines Register‘s Iowa Poll, which, not surprisingly, continue to show a competitive contest. Let’s briefly revisit where things stand just two days before caucus-goers make their preferences known.

The DMR poll effectively shows two tiers: three top-tier candidates who stand a chance of winning in Iowa (Romney at 24%, Paul at 22%, and Santorum at 15%), and three second-tier candidates who hope Iowa doesn’t derail their entire campaign (Gingrich at 12%, Perry at 11%, and Bachmann at 7%). It’s counter-intuitive, but the order of the bottom three may very well end up mattering more than the order of the top three — Santorum will get a boost no matter where he ends up in the top tier, while poor showings among the second-tier candidates may knock one or more candidates out of the race altogether.

Also note, of course, that there’s still room for even more changes — Santorum was third overall, but as the Register‘s pollster, J. Ann Selzer, noted, he was a very strong second in the final two days the poll was conducted. The possibility of Santorum winning Iowa now seems perfectly plausible.

Alexander Burns’ observation last night also rings true:

The poll is obviously good news for Mitt Romney as well as Santorum, and a late, authoritative survey like this one can also end up being a self-fulfilling prophecy as voters narrow their options to a subset of candidates viewed as possible winners.

Right. More than 40% of likely caucusgoers “say they could still be persuaded to change their minds,” and given the number of social conservatives in Iowa, talk of the late “Santorum surge” could very well produce a snowball effect. One of the main problems plaguing Santorum for months was the impression that his campaign just wasn’t going anywhere — and now that he’s the talk of the town, it seems more than likely that the former senator will not only pick up some late undecided Republicans, but also support from Perry and Bachmann, who are competing for the same GOP constituencies.

And what about Romney? By all appearances, the former governor is feeling very confident about his chances in Iowa, and he clearly goes into Tuesday as the apparent frontrunner, but even his support comes with caveats. Remember, Romney dropped the pretense weeks ago about whether he’s competing to win in Iowa, and he’s now invested considerable amounts of time, money, and energy to come out on top. And yet, even after Romney has made these efforts in Iowa, and become the clear frontrunner at the national level, he still can’t break his 24% ceiling, and his support is effectively at the same level as it was in October.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.