BURSA, Turkey — The cries tumbled from a balcony as Prime Minister Recep Tayyip Erdogan swaggered down the campaign trail in this picturesque industrial city and former Ottoman capital. “Papa Tayyip!” went the refrain, drawing a wry smile from the man himself.

The words may have lacked the weight of “Father of the Turks,” the title given Mustafa Kemal Ataturk after he established modern Turkey in 1923. But it said much about Mr. Erdogan — arrogant and populist to detractors, charismatic and visionary to supporters — who will soon enter his second decade as leader of a country he has helped transform.

As Turkey heads to an election on June 12 — the size of Mr. Erdogan’s majority the only question — the country faces an Arab Spring, which took it by surprise; ambitions that stretch beyond its means; and growing fears that Mr. Erdogan’s eight years in office have decisively shifted power from the old secular elite and toward his party and the merchant class, migrants and downtrodden that it courts.

But even his critics acknowledge that this country of 79 million is a far different place from the one he inherited, emerging as a decisive power in a region long dominated by the United States.