The fast-emerging split between the former allies is perhaps most clear in Syria, where Turkey and Iran now have dramatically opposing views about the repressive actions of President Bashar al-Assad.
On Tuesday, Turkish Prime Minister Recep Tayyip Erdogan praised the months-long uprising in Syria, calling the 3,000 who have died there at the hands of security forces "martyrs."
"The Syrian people will achieve results from their glorious resistance," Mr. Erdogan said. "Democracy will show its true self in Syria. Justice and freedom will be obtained by the Syrian people by their own will."
Yet until the Arab Spring took root earlier this year, Turkey had been cozying up to authoritarian powers with little apparent regard for the regional "democracy" that it espouses today.
In 2009, Syria's president and his Turkish counterpart affectionately called each other "brother." Erdogan said Syria is "our second home" and Assad hailed their "joint future" as a model of "brotherly ties." But Turkey's top priority appeared to be economic and political connections, not yielding to the popular will.
"Turkey had gone overboard in making these kind of gestures," says Ersin Kalaycioglu, a political scientist at Sabanci University in Istanbul.
"Earlier, the only major forces that Turkey supported were the anti-Israeli, relatively radical forces such as Hamas," says Mr. Kalaycioglu. "Now that democracy is a rising force, Turkey seems to be shifting grounds, ditching [Libyan leader Muammar] Qaddafi first, and then Bashar al-Assad, and also supporting developments in Egypt as much as possible."
On many fronts, Turkey's rhetoric – including its increasingly strident anti-Israeli views – had prompted Western analysts to question whether the NATO ally was forsaking its pro-West outlook to join the Iranian-led axis of resistance.