ISTANBUL • If there were a global contest for winning elections, Turkey's President Recep Tayyip Erdogan would see himself as the undisputed - and undefeated - heavyweight champion of the world.
In the 15 years since his ruling party came to power, Mr Erdogan has taken part in 11 elections - five legislative polls, two referenda, three local elections and a presidential vote - and won them all.
His victory on Sunday is his 12th and arguably his biggest ballot-box challenge since his ruling Justice and Development Party (AKP) came to power in 2002.
Fighting for votes in every corner of the country, Mr Erdogan kept up a punishing schedule of daily rallies, seeking to woo doubters with his indefatigable campaigning.
Prowling around the stage like a rock star, a wireless microphone in his hand, Mr Erdogan bellows at the crowds: "Do you want a strong Turkey?"
Known to his inner circle as "beyefendi" (sir) and to admirers as "reis" (the chief), he is supreme on stage, holding the audience's attention with near-matchless public speaking skills.
Mr Erdogan came to the referendum after the most turbulent year of his political life, which saw a slew of terror attacks, worsening relations with Europe and, above all, a failed coup on July 15.
With the new Constitution likely to come into force after elections in November 2019, Mr Erdogan could stay in power until 2029, by which time the energetic President, now 63, would be 75.
He seems determined to leave a legacy at least as significant as that of Turkey's modern founder, Mustafa Kemal Ataturk, whose picture hangs next to his at rallies.
Mr Erdogan has embarked on a hugely ambitious drive to modernise Turkey's infrastructure with a new bridge and two tunnels spanning the Bosphorus, high-speed trains and the construction of a third airport for Istanbul - schemes he affectionately refers to as "my crazy projects".
But critics worry about a creeping Islamisation of Turkey's officially secular society, with a surge in mosque-building, use of Islamic schools and the abolition of all restrictions on the headscarf in public life.