“You’re seeing a pretty clear indication that there will be a focus on the enforcement of our trade agreements and on the letter of the law,” said Scott Lincicome, an international trade lawyer at White & Case. “But that doesn’t necessarily mean a significant turn toward protectionism. Even free trade guys like me support enforcement.”

Trade opponents on the left and the right, meanwhile, are hoping Mr. Trump means to break with several decades of pro-trade policy.

“There’s going to be a war within the Trump administration on where they go with trade, and we’re hoping to energize the worker base he had to make sure they go in the right direction to benefit the American worker,” Mr. Trumka said.

Mr. Trump’s promise to immediately designate China as a currency manipulator may offer an early test of the administration’s intentions. Economists see no evidence China is suppressing the value of its currency, although it has done so in the past. Mr. Lincicome said officially labeling China a currency manipulator despite the lack of recent evidence would signal that the administration is taking a hard line on trade issues.

A broader shift in trade policy would unfold more slowly. Mr. Trump has promised to renegotiate Nafta; the original process took most of three years. He has promised to pursue enforcement actions against other nations, but it takes time to mount cases. He has threatened to impose new tariffs on imports, but sweeping changes most likely would require congressional legislation.

Mr. Trump already is seeking to exert influence by seizing the presidential bullhorn.

“General Motors is sending Mexican made model of Chevy Cruze to U.S. car dealers-tax free across border,” he wrote Tuesday on Twitter. “Make in U.S.A. or pay big border tax!”

General Motors announced in 2015 that it would make the Cruze in Coahuila, Mexico. American manufacturers are moving small-car production to Mexico to take advantage of lower labor costs and because of declining domestic demand. They continue to build more expensive vehicles in the United States.