Turkish voters go to the polls Sunday to cast their ballots in a constitutional referendum which could grant President Recep Tayyip Erdoğan sweeping new powers.

Polls show a neck-and-neck race, although recent surveys reportedly reveal a small lead for the Yes campaign.

At issue is whether to replace Turkey’s parliamentary model of government with a presidential system, giving Erdoğan executive powers and making him both head of state and head of government — on paper, like the presidents of the U.S., Mexico or Cyprus.

The referendum is so close that Turks in Europe could be the deciding factor. The importance of courting the Turkish diaspora was highlighted last month when Erdoğan got into a diplomatic feud with several European countries and compared German and Dutch officials to Nazis for not allowing Yes rallies to take place in their countries.

The vote, described by European commissioner for neighborhood policy and enlargement negotiations, Johannes Hahn, as "a departure from Europe" — is being closely watched in Brussels and elsewhere and could have ramification abroad, including for the Cyprus reunification talks.

POLITICO has covered many of the angles — here are some of our must-reads.

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Erdoğan’s power grab

A primer on the constitutional referendum — the most radical political change since the modern republic’s foundation in 1923 — that explains what is in the reform package and what it would mean for Turkey.

Turkey’s lose-lose referendum

Erdoğan will pursue his march toward one-man rule no matter the outcome of the April vote, argues Sevgi Akarçeşme in this opinion piece.

Turks abroad play pivotal referendum role

More than 1.4 million people have already cast ballots in the referendum on whether to grant the president more power. And they could be the deciding factor. Esther King went to Rotterdam, where Erdoğan supporters rioted in front of the Turkish consulate last month, to gauge the mood.

Erdoğan, the new Atatürk

A nearly century-old reverence for the father of modern Turkey is being replaced by a doctrine shaped by and centered on its president. A tale of a nation under attack from sinister outside forces — be they terrorists, coup-plotters or the often-invoked “interest rate lobby” — casts Erdoğan as the only leader capable of defending Turkey, cementing his power.

This narrative also serves as the backbone to a dramatic shift in Ankara, helping replace Turkey’s century-old official ideology — Kemalism, named after Mustafa Kemal Atatürk, the founder of the modern republic — with an ideology shaped by and centered on Erdoğan.

Renegade ultranationalists could derail Erdoğan

Meet Meral Akşener, a 60-year-old veteran of Turkish politics, whose outspoken defiance of Erdoğan has thousands flocking to her rallies across Turkey. She is one of a small band of renegade ultranationalists who may hold the key to the president’s ambitions.

The case against Turkey

Kati Piri, the European Parliament’s rapporteur on Turkey, writes that a visit to Ankara yielded no reasons to reconsider freezing accession talks.

"Talking about Turkey joining the bloc under current circumstances would lack credibility — especially in the wake of Erdoğan’s unwarranted accusations that German and Dutch governments were following 'Nazi practices.' Turning a blind eye to the Turkish government’s behavior would send the wrong signal to other candidate countries, of which the EU demands a strict adherence to European democratic values," Piri writes in this opinion piece.

Welcome to the Erdoğan fan club

In Europe, Erdoğan’s enduring popularity mystifies most politicians, and his increasingly authoritarian behavior eclipses any such previous successes — a disconnect that is becoming ever more pronounced.

But many Turks credit their president with shedding restrictive policies such as the headscarf ban, boosting the economy and, crucially, bolstering Turkey’s democracy by bringing an end to the military’s influence on politics.

Cyprus united ... over Erdoğan

With time running short, Cyprus needs a strong, secure Turkish president to back a deal to reunify the island, reports Sara Stefanini. "Paradoxically, if he wins the referendum — which is a blow to democracy in Turkey — it nevertheless may have a beneficial effect on the negotiations," is how one observer puts it.

How Erdoğan will derail Cyprus’ reunification

Turkey’s president will become more, not less, beholden to nationalist voters as he consolidates power, argues Mujtaba Rathman in this opinion piece.