It became the main route for those crossing to Europe, with thousands boarding dinghies every night from the Turkish coast to the Greek islands, and many drowning en route.

Government supporters remain convinced that anti-Erdogan bias in the West is misconceived and point out that Turkey is - among other things - the world’s largest host of refugees.

Turkey struck a deal with the EU to stem the flow - sending failed asylum seekers back. It’s widely believed that European leaders have tempered their criticism of Erdogan because they needed his co-operation on migrants.

But in some Western capitals, anger at Turkey’s unpredictable leader is growing. The European Parliament called for a suspension of EU membership negotiations.

In Turkey, this referendum will be a turning point. A “yes” would greatly strengthen Erdogan’s hand, giving him unprecedented power and possibly allowing him to remain in office until 2029, as well as virtually guaranteeing him and his family immunity from any attempts at prosecution.

A “no” would not spell the end for him - but would embolden the Turkish opposition and provide a chance for a political challenge.

Whichever way it goes, the chasm between Turkey and the West has grown dramatically.

Some blame Erdogan for that but others see the fault with the EU - that it had a window of opportunity after opening negotiations in 2005 to coax Erdogan into long-lasting reforms.

Instead, the argument goes, the EU gave way to the rhetoric of the likes of France’s Nicolas Sarkozy, who called Turkish membership “unthinkable”.

Turkey sensed it would continue to be held in the EU’s waiting room.

“Sadly, Europe sees President Erdogan and Turkey as an ‘other’ through which to deflect their internal problems onto a distant and imaginary enemy,” wrote Ibrahim Kalin, the president’s spokesman.

“It only deepens the sense of mistrust that is already poisoning relations between Turkey and Europe on the one hand and Islamic and Western societies on the other.”

Turkey matters. It remains a vital Western ally in the region, Nato’s eastern flank and a big trading partner. It is a crucial player in attempts to bring peace to Syria and the war against so-called Islamic State.

As it tries, with faltering success, to pivot more towards Russia and Gulf States, that could have a considerable geopolitical impact. The West cannot afford to lose this country.

“Democracy is like a train, Erdogan once famously said. “You get off once you have reached your destination.”

Some believe he has many stations left to pass, others that this country is in the midst of a slow-motion train crash. This could be the crowning moment or the undoing of Erdogan’s Turkey.