Des Moines, Iowa — A week after the 2012 election, Senator Marco Rubio of Florida flew here to headline a birthday party for Republican governor Terry Branstad. The venue was packed and the speech was a success. Charming and warmly received, he netted the governor more than $600,000.

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.”

Rubio’s latest Iowa headache is Sam Clovis, a charismatic, suspenders-wearing Republican running for U.S. Senate. On the campaign trail, Clovis frequently uses Rubio as a target. Rather than hit President Obama, the usual rhetorical punching bag, he slams Rubio on immigration to score points with conservatives. He does the same on his website, where he “shames” Rubio in a video.

In an interview, Clovis explains his attacks. “What he did is not sitting well with most of us in flyover country,” he says. “He’s the face of this bill, so I bring him up when I talk about the rule of law, and how these Republicans in Washington want us to violate our principles.”

The blows have taken a toll. Earlier this month, a Public Policy Polling survey of Iowa Republicans showed Rubio dropping among the field of likely contenders. After a long time near the top of 2016 tracking polls, he has sunk to fifth place, behind Senator Rand Paul of Kentucky, New Jersey governor Chris Christie, Representative Paul Ryan, and former Florida governor Jeb Bush.

Iowa insiders say it’s unlikely that Rubio will rise in the polls anytime soon, as long as immigration remains a hot issue in Congress. The chief reason cited, beyond the AM-dial blasts, is Steve King.

King, a conservative congressman from northwest Iowa, is a leading critic of the Gang of Eight, and his battle against amnesty dominates the Iowa political conversation. “King sucks out the oxygen, so maybe it’s best that Rubio stays out of here right now,” says an Iowa GOP official. “You can’t beat King when he’s on his home turf.”

In the meantime, sources close to Rubio say he’ll continue to work behind the scenes, repairing relations and seeking allies. He huddled with Bob Vander Plaats, an influential Iowa evangelical, earlier this year at a conservative conference in Maryland, and he has placed private, off-the-record calls to a handful of his Iowa critics.

team is also quietly building political contacts within the Hawkeye State. Todd Harris, Rubio’s political strategist, is advising U.S. Senate candidate Joni Ernst, a well-liked state senator from southwestern Iowa.Not everyone in Iowa Republican circles, however, believes Rubio is finished — starting with the governor. “It’s far too early to make a call on that,” Branstad tells me. “Rubio made a good first impression when he was here, and Iowans are pretty open-minded and fair.”

“You can’t start writing the script for the caucuses this summer,” says David Kochel, a strategist for Mitt Romney’s Iowa campaign. “Rubio may be getting heat, but he’ll get a substantial amount of credit, too, for doing something to fix a broken system.”

Doug Gross, a former Iowa GOP gubernatorial nominee, agrees. “All of this criticism toward Rubio is coming from a few extremists who don’t represent the whole party,” he says. “Marco Rubio is a good man and principled conservative, and he’ll have strong support.”

“I actually just invited Paul Ryan to speak at my birthday party this year,” Branstad says. “I think he and Rubio are the key leaders on immigration. I like both of them, and the issue is still being played out.”

If Rubio is planning to invest heavily in an Iowa campaign in the coming years, Branstad had better be right.

— Robert Costa is National Review’s Washington editor.