FRANKFURT — Turning a French carmaker and its German rival into a global auto giant would be tough under any circumstances. But the deal by PSA Group of France on Monday to buy General Motors’ Opel and Vauxhall brands has the added complexity of politics.

Political leaders, facing a rise of right-wing populism, are increasingly willing to meddle in the kind of difficult business decisions that will be necessary for the deal to pay off.

There has been a surge in government intervention in places like Italy, where bank-rescue rules have been bent to protect middle class savers. In Britain, Theresa May, the Conservative prime minister, has been talking about “an industrial strategy” — previously the province of left-wing Labourites. France has blocked foreign acquisitions of its companies.

Politicians have become acutely aware of how corporate decisions can create the resentments toward immigration and globalization that fed Donald J. Trump’s rise in the United States, contributed to Britain’s vote last year to leave the European Union, and nourished far-right politicians in France and Germany.

To make the deal work, PSA will have to navigate elected officials and labor leaders in three countries where it has big plants — Britain, France and Germany. The focus of the deal has already been heavily centered on saving jobs. In a conversation on Sunday with the chief executive of General Motors, the British prime minister emphasized the need to protect the plants and the homegrown brand, Vauxhall.

Car companies provide particularly fertile ground for nationalist appeals. The closing of a car factory is often devastating for the surrounding community, and it can fall hardest on less-educated, lower-income workers who feel neglected by elites and victimized by global finance.

And car manufacturers are often entangled with national identity. Opel, which has belonged to G.M. since 1929, is based in Rüsselsheim, near Frankfurt, and it is widely perceived as a German brand. PSA, the maker of Peugeot and Citroën cars, is 14 percent owned by the French government.

“What better industry to express a view of ‘France first’ than the auto industry?” said David J. Herman, who was chief executive of Opel in the 1990s. Making the acquisition work, he said, “is going to be excruciatingly difficult.”

Adding to the political tension, France and Germany have national elections this year.

In France, Marine Le Pen of the far-right National Front has an outside chance at winning the presidency in May. Ms. Le Pen has sought in her campaign to capitalize on high unemployment, calling for “targeted protectionism” and “economic patriotism” for French companies.

In Germany, which will hold elections in September, Frauke Petry and her Alternative for Germany party are trying to win at least 5 percent of the vote, the threshold to seat a delegation in Parliament. Ms. Petry’s party has tried to cast the sale of Opel in nationalist terms. Last month, Paul Hampel, a member of Alternative for Germany’s national governing board, called the deal a “sellout of German know-how.”

At a time when European unity is under threat, the sale of Opel to PSA could strain relations among Britain, France and Germany as they try to ensure that any pain is imposed…