Mr Recep Tayyip Erdogan, the towering figure in Turkey's politics this century and once the great hope for a marriage of Islam and democracy under EU wedding vows, seems narrowly to have won Sunday's referendum rewarding his quest for one-man rule.
The result was narrower than his strategists expected, and is being contested by a divided opposition that struggles to represent that half of the populace hostile to the Erdogan prospectus. The main opposition, the social democrat and secular Republican People's Party (CHP), is demanding a recount of more than a third of the votes.
The referendum, to approve or reject 18 amendments modifying 50 articles and repealing 21 others in a 1982 Constitution drafted by the army, can be made to sound almost pedantic. But the alterations proposed constitute a vast change. Mr Erdogan will be able to rule unchecked by any real balance of powers - making him more powerful than anyone before except for Mustafa Kemal Ataturk, who fought European predators to reassemble Turkey as a republic in 1923 after the collapse of the Ottoman Empire.
Mr Erdogan, who has won more than 10 elections since 2002 and ascended from premier to president in 2014, anticipated constitutional change by transferring power from the prime minister's office to what had been a largely ceremonial presidency. Now he will absorb powers currently exercised by Parliament and Cabinet, and will all but control the judiciary. The post of prime minister will disappear.
In strict legal terms, Mr Erdogan can only exercise most of these new powers after the next general election, not due until 2019. But too many sticklers for the rule of law are in jail for that to be a serious consideration.
Since last summer's bloody but abortive coup attempt by a hitherto allied Islamist faction inside the army, the government has jailed around 40,000 people and fired or suspended more than 130,000: generals and police officers, judges and academics, teachers and civil servants. Some 200 media outlets have been closed and 153 journalists jailed. Leaders and a dozen MPs from a left-wing party supporting the Kurdish minority are behind bars.
Mr Erdogan's neo-Islamist Justice and Development Party (AKP), which has never shaken off its opposition mindset in the identity contest with the now much-reduced secular establishment left by Ataturk and his army, is always on a war footing, headed towards the next election showdown. The quest for the Holy Grail never ends.
This one-sided contest, where Mr Erdogan held all the campaigning cards from control of the streets to monopoly of the airwaves and censure of social media, further polarises a deeply divided Turkey. The President's Anatolian heartland of unconditional supporters is largely intact. But metropolitan and coastal Turkey, strongholds of the secularist and Kemalist "white Turks", along with the mainly Kurdish south-east and east devastated by the resumption of war with the Kurdistan Workers' Party (PKK) purporting to represent Turkey's minority Kurds, all voted no.
Many questions face Mr Erdogan, now that he seems to have reached his goal of untrammelled power. Turkey's European Union and Nato allies also have decisions to make.
Does Mr Erdogan intend to govern against, or on behalf of that half of the population which keeps voting against him? Will he, for instance, renew the state of emergency, through which he already governs by unbridled decree, due to expire this week?
After purges since last July's putsch, which he blames on infiltrators inside the state loyal to cleric Fethullah Gulen, an Islamist imam and his ally for over a decade, will Mr Erdogan explain what happened, and stop using the coup as a pretext to treat all opponents as traitors or terrorists?
Turkey's Western allies need to make up their minds, too, in the light of Mr Erdogan's autocratic behaviour. The EU is beholden to Turkey to hold back further surges of refugees from Syria and Iraq. But can it maintain any longer the fiction that Mr Erdogan's Turkey is a candidate for EU membership? The US and Nato have mostly swallowed their frustration about Turkey's half-hearted commitment to fighting the Islamic State in Iraq and Syria, in order to keep using the Incirlik airbase in southern Turkey. Patience is running out.
Mr Erdogan's vaunted "New Turkey" has a vulnerable economy, closely integrated with Europe. It needs the EU and longstanding Nato and Western ties. Tense months lie ahead, at home and abroad.