RINGSTED, Iowa - Sen. Ted Cruz turned up the heat on Marco Rubio on Friday after the Florida senator's strong debate performance set him up as an unexpected threat to Cruz just three days out from the Iowa caucus.
After weeks of attacking front-runner Donald Trump, Cruz heightened attacks on Rubio's efforts at immigration reform and launched an attack ad on the issue too, just hours after stumbling to explain his own past and present immigration stances in the seventh Republican presidential debate.
"If we're tired of getting burned with politicians who claim to be against amnesty, who campaign against amnesty and then go to Washington and join the Democrats to support amnesty, then we need to look if they have a proven record," Cruz said Friday morning to a packed bar where his surrogates warmed up the crowd by telling them Rubio had done just that.
In the wake of a debate in which Cruz's performance was panned - notably on the front page of the Des Moines Register - the Texas senator retreated to northern Iowa, campaigning across the district that elected Rep. Steve King, the far-right conservative known for inflammatory remarks, like the Supreme Court's gay marriage ruling legalized wedding a lawnmower and young immigrants brought here illegally by their parents are mostly drug mules.
"Marco Rubio has gone on Univision and said in Spanish, 'No, no, I wouldn't rescind amnesty," Cruz said later, presumably referring to an interview Rubio gave in Spanish - the translation of which conservatives have debated - during which he said he wouldn't suddenly end the executive action delaying the deportation of young immigrants who were brought here illegally as children, but would work to replace it with a more permanent solution and felt the executive action should be ended.
Cruz's campaign confirmed to MSNBC that they'd also launch an attack ad against Rubio in the final hours before the caucus; the ad focuses on immigration and is one of three ads the campaign will run this weekend. (The other two are positive ads about Cruz.)
Cruz clinged to King's endorsement in Thursday night's debate - something Jeff Patch, an unaligned Republican operative who attended Thursday's debate, said was a peculiar move.
"King is not particularly well-known or followed in central or eastern Iowa," said Patch. "I thought it was a little weak that [Cruz] continued to rely on Steve King rather than rely on policy issues."
He agreed that Cruz struggled in the debate.
"It seemed at least in the room that that was definitely not Ted Cruz's crowd," he said, noting the moment when the audience cheered for Gov. Branstad, who last week urged voters to caucus for anyone but Cruz. Still, Patch said he didn't see any "major stumbles" and that Cruz seemed to be focused more on mobilizing his base - not converting new voters.
While the general consensus among Republican strategists was that Cruz underperformed in the final GOP debate before the Iowa caucuses, particularly when it came to explaining his past positions on immigration and current opposition to the renewable fuel mandate, some said it wasn't a campaign-ending flop.
"Because Mr. Trump wasn't there, Cruz was going to be criticized more," longtime Iowa strategist Eric Woolson, who was involved in Wisconsin Gov. Scott Walker's brief bid for the presidency this election cycle, told MSNBC. "It was a kind of self-fulfilling prophecy."
Rubio told reporters on Friday afternoon that the attacks were a sign of his success.
"When a candidate's being attacked, obviously someone's worried about you, so obviously Sen. Cruz is worried about my candidacy," Rubio said across the state in Muscatine. "I think people are starting to learn that the truth about Ted on immigration, and a bunch of other issues shows the history of calculation. And I think it's starting to hurt him a little bit."
This article originally appeared on MSNBC.com.