ANKARA, Turkey — With his victory in Sunday’s elections, President Recep Tayyip Erdogan has taken his place among the world’s emerging class of strongman rulers, nailing down the sweeping powers he has insisted he needs to address Turkey’s numerous challenges, at home and abroad.

Now, all he needs to do is deliver.

“He won on a knife-edge,” said Ugur Gurses, a former banker who writes for the daily newspaper Hurriyet. “But now he has in his lap all the problems.”

Mr. Erdogan is contending with an array of economic troubles, an increasingly disgruntled populace and deteriorating relations with Turkey’s Western allies. Among the many problems Mr. Erdogan faces is one fundamental roadblock: His foreign policy is fighting with his economic needs.

His increasingly authoritarian, nationalist and anti-Western bent is alienating foreign investors, which is hurting the Turkish lira. As the currency plunges, domestic capital flees. And he is newly reliant on a nationalist party that enabled him to maintain his majority in Parliament but promises to reinforce all those tendencies, as well as his hard line against the Kurdish minority.