Turkey votes on Sunday in a referendum on vastly enlarging the powers of the presidency under Recep Tayyip Erdogan. The result could change the country’s parliamentarian system of governance into a presidential one, influencing all aspects of the country’s future.

The vote, in which millions of Turks will decide whether to replace their parliamentary democracy with an all-powerful presidency, may bring the biggest change in their system of governance since the modern Turkish republic was founded on the ashes of the Ottoman Empire almost a century ago.

Coming 94 years after the foundation of modern Turkey by Mustafa Kemal Ataturk, the referendum is a landmark vote that may affect relations with the West, a peace process with Kurds and dynamics inside Turkish society.

If he wins the referendum, Erdogan will enjoy enhanced powers, be able to appoint ministers and have an entire bureaucracy centralised within his presidential palace. Opponents worry that the new system will lack the “checks and balances” that mark the US system, moving the presidency toward one man rule.

The new system would be implemented from November 2019 when presidential and legislative elections would be held simultaneously.

With the clock wound back under the new system Erdogan, who became president in 2014, could take two more terms, allowing him to stay in power until 2029 rather than 2024, currently.

Relations between Turkey, a longstanding candidate to join the European Union, and its EU partners plunged to bitter lows during the referendum campaign as the president lashed out at Europe for what he said was behaviour reminiscent of Nazi Germany.

Never in recent times has Turkey, one of only two Muslim members of the NATO military alliance, been so central to world affairs, from the fight against Islamic State in Syria and Iraq, to Europe’s migrant crisis and Ankara’s shifting allegiances with Moscow and Washington.

The campaign has split the country of 80 million down the middle, its divisions spilling over to the large Turkish diaspora in Europe.

Erdogan assumed the presidency, then a largely ceremonial position, in 2014 after more than a decade as prime minister, and has since continued to dominate politics by force of personality, making no secret of his ambition for greater powers.

He has ridden a wave of patriotism since an abortive coup in July, casting Turkey as at peril from a cocktail of outside forces and in need of strong leadership to see off threats from Islamic State, Kurdish militants, the enemies within who tried to oust him and their foreign backers.

A poll two weeks after the attempted putsch showed him with two-thirds approval, his highest ever, but more recent surveys suggest a much closer race. A narrow majority of Turks will vote “Yes”, two opinion polls suggested on Thursday, putting his support at only a little over 51 percent.