It’s safe to say Rick Perry has given up his perch as the Republican presidential frontrunner. In fact, the apparent collapse happened rather suddenly, with a debate in Florida marking the pivot point. Almost immediately, the question in GOP circles went from, “Is Perry too conservative to win in a general election?” to, “Does anyone have Chris Christie’s phone number?”

But some of the analysis of Perry’s sudden decline has been off the mark over the last two weeks. I’ve seen more than a few pundits suggest that one debate performance ruined Perry because he seemed like such a lightweight — ignorant, inarticulate, and unlikable.

Those assessments are fair, but it’s not what’s dragged Perry down. Immigration is.

Rick Perry has an immigration problem. In all three of his appearances in Iowa on Saturday, voters pressed the Texas governor and GOP presidential candidate on the issue, specifically his decision to grant in-state tuition to the children of illegal immigrants.

Perry has acknowledged that he made a mistake when he referred to people who opposed his policy as heartless during a debate last month. But he has stood fast on his decision to grant the tuition break in Texas.

Responding to voters’ questions here, Perry argued that in Texas, helping the children of illegal immigrants was a way to create “taxpayers, not tax-wasters.” He assured one questioner that there were “no free rides” in Texas for the children of illegal immigrants, although the dispute is over whether to grant reduced in-state tuition, not free college, for illegal immigrants.

And Perry emphasized that in Texas he opposed legislation that would have allowed illegal immigrants to get driver’s licenses and supported a provision that requires Texans to show some form of identification to vote.

But it’s not working. For one thing, the “have a heart” comment during the debate lingers, and offended the right in a rather fundamental way (they hate it when the left makes the accusation, but they really hate it when it comes from one of their own). For another, Perry backed off the “heartless” rhetoric, but he hasn’t flip-flopped on the policy itself.

And as a result, as Politico noted, “Perry’s immigration problem isn’t going away. It’s getting bigger.”

At a certain level, it may seem ridiculous that a right-wing Texas governor and one-time frontrunner would be brought down by such a mundane issue — in-state tuition rates for kids who live in the state. But far-right activists are in an unforgiving mood; their disgust for undocumented immigrants has only intensified in recent years; and Perry hurt their feelings with the whole “heartless” comment.

Mitt Romney seems far more willing to simply tell the Republican base whatever they want to hear, and pretending his record simply doesn’t exist. It may very well mean the difference between winning the nomination and losing it.

Steve Benen

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.