WASHINGTON — Republican leaders had muscled through their failure to repeal the Affordable Care Act, punted on the perennial brinkmanship over the debt ceiling and finally reached the one issue that all of the party’s factions wanted to be on, tax reform.
Then, over a Chinese dinner at the White House with the two top Democrats on Capitol Hill, President Trump threw that momentary sense of satisfaction into disarray, forcing Republicans to confront the subject that packs more emotional and political force than anything they had on their busy agenda: immigration.
Virtually nothing can drive Republicans more bitterly apart than immigration policy, which has vexed the party ever since President Ronald Reagan signed the Immigration Reform and Control Act of 1986. Republican leaders were scorched by the issue when President George W. Bush pushed it in his second term. The divisions re-emerged when President Barack Obama took it back up.
And now it re-enters the political bloodstream just when the party was desperate to demonstrate its ability to deliver on other complicated issues before lawmakers face voters next year, like lowering corporate and individual tax rates and revitalizing the nation’s infrastructure.
Mr. Trump’s tentative agreement on Wednesday with Senator Chuck Schumer of New York and Representative Nancy Pelosi of California to move forward on legislation to protect the legal status of young, undocumented immigrants and to delay, for now, a fight over the president’s promised border wall triggered anger and bewilderment on the right.
From talk radio studios to the halls of the Capitol, conservatives across the ideological spectrum seemed caught off guard by the president’s move, unsure what exactly he had agreed to, if anything at all.
“No one knows what the deal is,” said Representative Mo Brooks, Republican of Alabama, who expressed wariness about the agreement and spared no one in his criticism. “I am frustrated with all of Washington, and I make no exception.”
On Twitter, the conservative firebrand Ann Coulter was more blunt: “At this point, who DOESN’T want Trump impeached?” Breitbart News gave the president a belittling nickname of his own: Amnesty Don.
Mr. Trump insisted at the White House on Thursday, “We’re not talking about amnesty at all,” and he tried to reassure rattled supporters that there would still be a wall. “The wall will happen.”
Still, he has put Republicans on an unpredictable path, compelled to take up immigration, not on their own terms but after the prodding of two Democratic leaders who are politically invested in their failure. If nothing else, no one seemed very interested in talking about tax policy on Thursday.
Mr. Trump’s former chief strategist, Stephen K. Bannon, told “60 Minutes” this week that by spring “it will be a civil war inside the Republican Party” if Congress sets itself on a path toward approving new immigration legislation.
The president is testing that prophecy.
“No promise is credible,” fumed Representative Steve King, Republican of Iowa and perhaps the leading proponent in Congress advocating the hard line on immigration that Mr. Trump has voiced. Mr. King tweeted, “Reagan led with Amnesty, 1986. Bush43 led with Amnesty ’06, Obama led with Amnesty ’13. All failed so…Trump leads with DACA Amnesty 2017.”
The odd new alliance over DACA, or Deferred Action for Childhood Arrivals, also threatened to scramble alignments within the already fractious Republican Party, suddenly giving the party’s moderates the upper hand.
“The roles are reversed,” said Travis Korson, a Republican strategist who has worked with conservative groups and lawmakers to forge a consensus on immigration.
Republicans who were wary of Mr. Trump’s tough talk on immigration and his demand for a border wall, Mr. Korson said, are open to a deal that offers legalization for the so-called Dreamers in exchange for more border security.
At the same time, Mr. Korson added, “Republicans who backed Trump during the campaign, in part because of the wall, are the ones most likely to split with him over this deal.”
“The question for them,” he said, is whether the wall will “be a hill they’re willing to die on.”
Most Republicans had assumed the president considered the wall nonnegotiable.
No promise was more central to his campaign. And no constituency was more passionate in defending Mr. Trump than the conservatives who believed he would be uncompromising in his approach toward illegal immigration. Just last month, he was threatening to shut down the government if Congress did not approve funding to start the wall’s construction.
Mr. Trump’s sudden embrace of politicians whom Republicans have spent years vilifying — especially Ms. Pelosi, whom Republicans have made into an avatar for the liberal, coastal elite — also sowed confusion. How could the party, some wondered, continue to persuasively demonize Democrats if their president is going behind their back to reach compromises with them?
“Republicans have spent so much time and money targeting Nancy Pelosi as the enemy over the last few cycles, the idea that you’re now going to do a deal with her has to rub people the wrong way,” said Russ Schriefer, a Republican consultant who has worked for George W. Bush and Mitt Romney. “Doesn’t it hurt all these Republican congressmen who want to use her as the liberal foil in their campaigns?”
The risks could be greater than a messaging issue. Many Republicans worry about the impact that disillusioned Trump supporters will have if many of them have concluded by next year’s elections that the president sold them out. If those voters stay home, that could cost Republicans their majorities in Congress.
Amid all the political controversy, legal peril and everyday disarray inside the Trump White House, Republicans whose fates are linked to the president’s have wondered how much more his base would tolerate. The president once boasted that he could “stand in the middle of Fifth Avenue and shoot somebody” and still not lose voters. With this immigration deal, he may finally have an answer to that proposition.
“I always figured Trump would go Schwarzenegger on us,” one caller into Hugh Hewitt’s conservative talk radio program said on Thursday, invoking the former California governor, who many conservatives believed sold them out.
Some listeners said Mr. Trump had confirmed what they suspected all along about the insincerity of his conservative convictions. Others said the president, a self-proclaimed master negotiator, had been rolled by the Democrats. The comments mostly added up to a damning conclusion: Mr. Trump had tricked his voters.
“The No. 1 reason I voted for him was for the immigration,” said a caller into Laura Ingraham’s show. “I want the wall. I want it to be seen in space, like the Chinese wall.”
Ms. Ingraham, who has until now been sparing in her criticism of the president, told her listeners on Thursday that the political cost to Mr. Trump and the Republican Party would be steep.
“He’s going to get creamed for this,” she said, reminding her audience of all the times during the campaign that Mr. Trump chanted — and his crowds repeated — “build the wall!” (Not since George Bush’s “Read my lips, no new taxes” pledge has one phrase been so synonymous with a campaign pledge.)
“I don’t remember hearing ‘Repair the fence! Repair the fence! Repair the fence!’” Ms. Ingraham added, mocking Mr. Trump’s attempt to defend himself by noting that parts of the current border fence were being repaired and reinforced under his direction.