Such transactions were attractive, because the lira was then appreciating and the Turkish economy was rapidly expanding. But in recent years, as the lira has fallen, companies with revenues in lira and debts in dollars have seen their burdens expand.

Turkey’s medium- and long-term foreign currency debts exceeded $328 billion as of the end of 2018, according to official data, with private companies responsible for about two-thirds. Private companies confronted a further $138 billion in foreign exchange debt due in the next year. Given that Turkey’s overall economic production was about $766 billion last year, these numbers were disturbing.

“I don’t think companies will be able to pay back their debts,” says Selva Demiralp, an economist who previously worked at the Federal Reserve bank in Washington and now teaches at Koc University in Istanbul. “It may spill over to the local banking system. They are the ones who are going to be on the hook for the bad loans.”

Some say the government has room to help companies in trouble. Officially, government debt last year amounted to a manageable 30 percent of annual economic output.

But Turkey’s financial workings are opaque and vulnerable to political manipulation. Mr. Erdogan has tapped state-owned banks to finance favored projects. Partnerships between the state and private companies have kept debts off government ledgers.

“These major projects, when they fail, it’s going to be the government that is going to have to bail them out,” says Mr. Hakura, the Chatham House expert. “The public debt numbers are a mirage.”

The savviest companies are exploiting weakness as an opportunity. Reha Medin Global, a real estate company with offices in a dozen Turkish cities, has seen domestic sales plunge given weak spending and mortgage rates running above 20 percent a year.