Turkish President Recep Tayyip Erdogan has prevailed in a referendum that will transform his country's political system. Given the razor-slim margin of victory, charges of voter fraud and complaints that the campaign was rigged against opponents of the referendum, the ballot is more likely to increase tensions in Turkey than vent them. It is not yet clear what the foreign policy implications of the vote may be, but international censure is unlikely to have much impact on Erdogan. The West must now prepare for an even more contested relationship with Turkey.

Despite — or perhaps because of — Erdogan's extraordinary political successes, he has bristled at institutional restraints on his power. Ever since he moved from the prime minister's office to the presidency in 2014, he has railed against the constraints he faced as he sought to modify Turkey's political system to give him more power.

The first proposal for a constitutional referendum to create a presidential system was made in 2005, when Erdogan was then serving as prime minister. The idea gestated until last December, when the ruling Justice and Development Party proposed 21 amendments to the national charter; that list was whittled down to 18, which went before voters last Sunday. The changes, the most important since the modern Turkish state was founded, will vest all executive power in the presidency, allowing him to appoint (or dissolve) a Cabinet, and hire and fire all judges and prosecutors, to name but two new prerogatives. They abolish the post of prime minister and limit the legislature's power to amend bills.