A survey conducted in early May for The New York Times by the online polling firm SurveyMonkey found that 78 percent of Republicans approved of Mr. Trump’s tariffs on steel and aluminum. A majority of independents and Democrats disapproved of the tariffs.

Mr. Trump’s tariff impositions and threats have drawn condemnation from top Republicans in Congress, but little legislative pushback. After Mr. Trump said last week that he would follow through on steel and aluminum tariffs against Mexico, Canada and the European Union, Speaker Paul D. Ryan of Wisconsin said he disagreed with the decision.

“There are better ways to help American workers and consumers,” Mr. Ryan said. “I intend to keep working with the president on those better options.”

Senator Mitch McConnell of Kentucky, the majority leader, said on Friday in Louisville that “I don’t think anything good will come out of a trade war, and I hope we pull back from the brink here.” But he said Republicans in Congress could do little to stop Mr. Trump’s actions.

“Under the trade law, the president has pretty much all the ability to do these things, so there’s not much we can do to impact it,” Mr. McConnell said. “It’s really an executive branch activity, and he’s got the authority to do what he’s chosen to do. It’s just that I think many of us feel that it shouldn’t be done.”

Republican leaders could try to counter Mr. Trump by working with Democrats to curb Mr. Trump’s trade powers. Senator Mike Lee of Utah has proposed such a bill, which Senator Patrick J. Toomey of Pennsylvania recently endorsed.

But Republican leaders appear to have little appetite for sweeping legislation. Instead, they seem content to advance more targeted measures, such as blocking the administration from softening its punishment of the Chinese telecommunications firm ZTE.