Since then, though, Rubio hasn’t been back, and his popularity among Iowa conservatives has dipped. A growing number of tea-party activists are irate about his efforts on immigration reform. Instead of being cheered at rubber-chicken dinners, he’s being slammed — and some Republicans say a run for the caucuses would be doomed.

“He has been seriously hobbled — we’re talking about long-term damage,” says Chuck Laudner, a veteran Iowa Republican who helped Rick Santorum win the 2012 caucuses. “Most conservatives feel burned, and he doesn’t have a lot of allies in the state defending him.”

Iowa’s talk-radio hosts have been particularly brutal. Steve Deace, an influential Christian conservative, has warned Rubio not to even show up, and has often taunted him during broadcasts. “Zip, zilch, nada — he’s got no support, he would be dead on arrival,” Deace tells me. “He may end up running for president, but he can’t win here.”

When I mention that Rubio could mount a comeback by pushing conservative initiatives on other issues, such as abortion, Deace is dismissive. “I don’t care how pro-life Rubio is,” Deace says. “If he’s pro-life, that’s great, but what he has done on immigration is unacceptable.”