One of the Trump administration’s most unpopular ideas, tacking tariffs onto automobile imports that would jack up their prices, might nonetheless accomplish what the president envisions: strengthening the competitive edge of the best-known American carmakers.

The reason: General Motors, Fiat Chrysler, and Ford have the most unused vehicle production capacity in the U.S., meaning they could respond more nimbly if President Trump’s 25 percent tariffs on imports prompted a drop in demand, said Colin Langan, an analyst with the Swiss lender UBS.