Protesters of Donald Trump's stance on immigration carry signs at a Trump campaign event at Marshalltown Community School District Roundhouse Gym in Marshalltown, Iowa, on Jan. 26. (Tannen Maury/European Pressphoto Agency)

DES MOINES — Last June, on the day that Donald Trump announced his presidential bid, Republican strategist Katie Packer issued a warning to her party.

"As deputy campaign manager of Mitt Romney’s 2012 presidential bid, I saw first-hand how the rhetoric on immigration during the GOP primary, from all of the candidates, painted our party in a negative light and came back to bite us in the general election," she wrote.

Sharing research conducted by her Burning Glass Consulting, Packer said that the Republicans using "harsh rhetoric that defines anything short of deportation as 'amnesty' " were actually doing a long-term disservice, "chasing the relatively small group of anti-immigration primary voters — and giving opponents ammunition to portray them as anti-immigration."

Seven months later, with Trump defying gravity in Iowa and the first primary states, Packer founded a super PAC designed to take him down. In the longest spot from Our Principles PAC, part of a $1 million buy here, a narrator asks if Trump is soft on immigration so he can use "illegal" labor to build his properties.

"Trump can't answer tough questions, like why he'd let millions of illegal immigrants stay in America, and even supports a pathway to citizenship," the narrator says.

"You have to give them a path, and you have to make it possible for them to succeed," says Trump in a clip from 2015.

The voters who have packed Trump's rallies have heard similar answers before. Trump typically twins his call for a border wall ("Mexico is going to pay for it") with a "big, beautiful door" to let in deserving immigrants. A Trump ad currently on the air in Iowa, which portrays Sen. Ted Cruz (R-Tex.) as two-faced on immigration, ends with Trump saying that the United States "needs borders," with no additional comments about what it should take to become a citizen.

But the Our Principles ad — part of a series that conservative radio host and author Erick Erickson pronounced "very effective" — comes from a tradition of "establishment" forces ceding defeat on an argument to sway conservative voters. In 2014, the Chamber of Commerce helped protect some Republican senators with ads that portrayed them as true conservatives, and their primary foes as slippery.

This year, in Iowa, voters have heard an establishment-friendly PAC warn them against "amnesty." In a 60-second spot from Right to Rise, a PAC supporting Jeb Bush that has spent $20 million attacking Sen. Marco Rubio (R-Fla.), conservatives are told that Rubio once favored "in-state tuition to illegal immigrants," and that he teamed with "New York liberal Democrat Chuck Schumer" on the 2013 immigration reform bill.

"Rubio ran for the Senate and promised to oppose amnesty," says a narrator. "But in Washington, Rubio broke his promise and joined with liberal Democrats to co-author the path to citizenship bill."

Bush supported the passage of an immigration reform bill in 2013, and wrote at the time that Rubio's bill did not "provide amnesty." And Mike Murphy, the strategist behind Right to Rise, told The Washington Post's Jennifer Rubin in 2014 that smart Republicans would favor reform, realizing that the short-term bursts of anger from talk radio paled before the potential loss of Latino voters.

"If voters really were anti-immigration reform, we’d be listening to President [Tom] Tancredo," Murphy said.

Neither the Right to Rise and Our Principles spots advocate for a particular candidate; the fridge-magnet-poetry-style of PAC names makes it harder for voters to link an attack to a source. But their aggregate effect is that any suggestion of a "pathway to citizenship" — something broadly favored by Republican and business elites — is being toxified again. Seven months ago, Packer urged her fellow Republicans not to go there.

"To grow our party — and win the White House in November 2016 and beyond — Republican candidates need to resist the temptation to characterize one another as soft on immigration," she wrote.

In a Twitter conversation today, Packer said that she stood by the 2015 essay, and that the ad was making a larger point about Trump's untrustworthiness.

"The point of the ad is, how can you trust a guy who says he's for amnesty, then says we need to throw them ALL out because they are a bunch of rapists and murderers, then two weeks later calls for a path to citizenship?" she asked. "He's a phony."

This post originally misstated the name of Katie Packer.