President Trump’s steel and aluminum tariffs provoked louder opposition from Republican congressional leaders than anything else the president has done so far, but GOP leaders have no plans to take the strongest action available to them to block the tariffs: pass legislation to overturn them.

“The thought that the president would sign a bill that would undo actions he’s taken strikes me as remote at best, and I like to use floor time in the Senate for things that actually have a chance to become law,” Senate Majority Leader Mitch McConnell (R-Ky.) told reporters this week at the Capitol. “So I think it’s highly unlikely we’d be dealing with that in a legislative way.”

It is a bow to political realities, including the difficulty of assembling veto-proof majorities to defy a president popular with core GOP voters Republicans need for November’s midterms. Alarmingly for some in the GOP, there are signs Trump is beginning to remake the Republican Party in his image, pushing voters and some lawmakers away from the party’s long-held support for free trade and toward the protectionist philosophy favored by the president himself.

To some, the moment represents a potential turning point for a Republican Party that has long espoused the free-trade philosophy shared by the business interests and donors that have constituted key elements of its core constituency. It also raises the possibility that Trump’s influence on the party will extend past his presidency and that the voters animated by Trump’s protectionist rhetoric may continue to demand that approach even after Trump’s name is no longer on the ballot.

“Certainly Donald Trump has taken over the Republican Party. The question is, has he taken it over on every issue?” said Rep. Charlie Dent (R-Pa.), a moderate Republican whose district once hosted major steel production facilities he says cannot be revived, tariffs or not.

There is evidence Trump has already helped engineer a significant shift in the Republican Party’s opinion on trade.

Last year, 67 percent of Democrats and Democratic-leaning independents said free trade agreements were a “good thing” for the United States, compared with 36 percent of Republicans and those leaning Republican, according to the Pew Research Center. In 2009, the partisans were close to agreement on the issue.

Positive GOP views of free trade crashed during the presidential election when Trump made opposition to trade a central campaign issue. While Democrats have long counted on the support of labor unions that opposed trade pacts such as the North American Free Trade Agreement, many union members supported Trump for president, more signs of a political realignment with promise and peril for both parties.

Legislation has been introduced to overturn the tariffs, and an upcoming must-pass spending bill also provides a vehicle to target them. But instead of moving to block the tariffs legislatively, GOP leaders have been working feverishly behind the scenes to get the administration to narrow its scope.

Trump last week formally unveiled a 25 percent tariff on steel imports and a 10 percent tariff on aluminum, though he granted initial exemptions for Canada and Mexico as they renegotiate NAFTA. Trump also said other allies could apply for exemptions, as well, suggesting countries that made other trade concessions might be spared.

Within the White House, divisions that preceded the tariff announcement continue to rage, with the fight now focused on how many exceptions should be made, according to two officials.

Trump, Commerce Secretary Wilbur Ross and others are fielding calls from top GOP lawmakers seeking more flexibility in the application of the tariffs and, in some cases, exemptions for specific companies in their states. Trump will basically say yes as long as they promise him something in return and do not criticize him, one senior White House official said.

Ross and White House trade adviser Peter Navarro have told Trump that if the exception is the rule, he will not be viewed as being tough enough. And Trump, in turn, says at times that they should not give many exemptions.

Staff for House Speaker Paul D. Ryan (R-Wis.) have pushed the White House to implement a formal process for exemptions, administration and Hill officials said. An established process would run counter to Trump’s statements that he’d have the power to alter tariff terms for individual countries at will. A Ryan spokesman declined to comment.

The speaker has repeatedly told the president he thinks the tariffs are a bad idea.

The White House has said privately that a more formal process will be created, but so far, there have been few signs of that happening, according to the officials, who spoke on the condition of anonymity to discuss internal discussions.

Trump had a call with House Ways and Means Committee Chairman Kevin Brady (R-Tex.) this weekend where the president reassured him there would be exemptions to the tariffs. Trump expressed “a lot of willingness to narrow the policy,” according to a person familiar with the conversation.

Brady declined to comment on any conversation with the president but told reporters Tuesday that he was hopeful that the administration was showing flexibility on the issue.

Lawmakers are also pushing Trump to grant exemptions for home-state companies that use large amounts of the metals. Sen. Ron Johnson (R-Wis.) described speaking with Ross this week to make the case that some Wisconsin companies would be badly hurt by the steep tariffs.

In Wisconsin farm country and elsewhere, there are also deep concerns about retaliation against U.S. agriculture exports, which had started after Trump had announced tariffs on solar panels and washing machines. “In my conversation with [Ross], he’s certainly aware of the challenges to steel-using industries like we have in Wisconsin, and they’re going to do everything they can to try to mitigate the unintended consequences of those,” Johnson said in an interview. “They’re aware of those, and they obviously don’t want to see collateral damage.”

Ross and his office have been flooded with calls to get exemptions. Wisconsin Gov. Scott Walker (R) called last week for Harley-Davidson and other companies.

Ross’s “phone is the busiest in the White House these days,” one senior White House official said.

Looming in the background of the debate over the tariffs is the prospect of Trump withdrawing from NAFTA, an outcome many Republicans say would be catastrophic. If there is a silver lining to be found in Trump’s approach on trade so far, they say, it is that thus far he has not done that.

But Trump is also considering a new, targeted set of tariffs on imports from China, threatening to upset a delicate relationship between the world’s two largest economies.

The shift in the overall Republican Party view on trade has forced congressional Republicans to recalibrate their tactics, whether in how they talk about the issue or in their resistance to endorsing legislation that would override the levies on steel and aluminum imports.

“Yeah, they’ll say, ‘I’m for free trade, but fair trade,’ ” Sen. Jeff Flake (R-Ariz.) said of the change in how Republicans are now messaging on trade. “It’s caveated more than it used to be. It’s tougher to find somebody who would just go out unabashedly and say, ‘I’m a free trader.’ ”

Flake, a Trump critic who is retiring from the Senate, has introduced legislation nullifying the tariffs, yet is realistic about the lack of political will in his party to counteract Trump’s trade moves. “Look at how reluctant Republicans have been to push back on anything that he can then go to their district or their state and campaign against them,” Flake said. “Unfortunately, it’s changing the party in ways that aren’t healthy for the party or for the country, frankly.”

Sen. John Thune (R-S.D.) said Trump is “probably moving the debate a little bit” on trade throughout the country.

“The populist appeal of America first, I think, resonates with a lot of folks who are kind of dispassionate about this issue,” Thune said. “But anybody who is engaged in industries that are dramatically impacted by trade — in my case being agriculture — they still see this with pretty clear-eyed concerns.”

Further complicating any efforts are pockets of the GOP conference who have enthusiastically backed Trump’s decision, especially among House members who represent steel and aluminum industries in their districts.

Rep. Mike Bost (R-Ill.) has been one of the few supporters among House Republicans, and he says it will benefit the steel industry in his southern Illinois district. “When I see my steel people continuing to lose their jobs, we’ve got to do something,” Bost said. The congressman added that Trump has a “unique perspective” on trade compared with other party leaders “because he’s experienced it.”

“He actually went out and talked to the people, and he saw what the people were suffering from,” Bost said.

“I think what the president has brought to the table . . . is that free trade for the sake of free trade no longer is the standard. It is free but fair and enforceable trade,” Rep. Tom Reed (R-N.Y.) said. “I think that comes from decades of us being left on the negative side of the equation when it comes to the trade imbalances representing Rust Belt areas of the country like myself.”

A number of Republicans say that in hindsight, they regret congressional decisions over the years to cede authority over trade to the executive branch. It is a system that worked well for the country for years, they say, since trade deals are better negotiated by a single chief executive than 535 members of the House and Senate. But now that it is too late, some would like to get some of that authority back.

“Frankly I think in the long run, it would be better if Congress had more of a role,” Thune said. “We kind of gave that away.”

Sen. Mike Lee (R-Utah) has introduced legislation that would give Congress approval power over trade decisions. Companion legislation is being written in the House. But the bills do not appear destined for a vote.

Before Trump, opposition to free trade in the general presidential election was largely the province of third-party candidates, as favor for broad trade deals was among the few economic threads that united both Bush administrations and former presidents Bill Clinton and Barack Obama.

Now, if Republicans back away from being the party of free trade, some Democrats see an opportunity for their party, historically more protectionist than the GOP, to seize the issue and turn it to their advantage in coming election cycles.

Yet Republicans’ skepticism on free trade in 2016 had a mirror movement in the Democratic Party, where primary candidate Sen. Bernie Sanders (Vt.) criticized trade deals and hammered Hillary Clinton for her support of them. Clinton, a longtime advocate of global economic integration, moved on the issue as well, eventually opposing as a candidate a massive trans-Pacific trade deal she had championed as Obama’s secretary of state.

Still, some Democrats see an opening. Terry McAuliffe, Virginia’s former Democratic governor, suggested last week that Democrats should reject protectionism and “focus on building a modern economy that competes globally,” he wrote in the New York Times.

“If in fact the Republican Party abandons its advocacy for open markets and freer and fairer trade, then that would represent a significant political realignment,” said Dent, the House Republican from Pennsylvania. “And the question is, what does the Democratic Party do?”