No logical person can understand why Erdogan has started a new round of turbulence in Turkey by targeting the mayor of Istanbul.

In what was (otherwise) a positive and significantly less tense situation for the Turkish president.

His regime seemed to have stabilised and he wasn’t under pressure. The economy had largely levelled out, albeit at a lower level than before.

The wounds left in the body of Turkish society by the earthquakes were healing. And the current geopolitical situation left little or no scope for any major domestic unrest.

Erdogan is in the middle of what should (constitutionally) be his final term, and one might expect him to be planning for the quiet life of a successful and long-lived former President rather than picking new fights.

Which is why his attack on the man who has the best chance of succeeding him, albeit in two and a half years’ time, is seemingly incomprehensible.

Only it isn’t, because this is Erdogan we’re talking about.

Because in his case, no one knows whether the Constitution applies, whether this is really his last term, and what he fears may await him when he has released his grip on power.

Don’t underestimate the latter. It may well be the most important factor of all.

No authoritarian and controversial leader retires peacefully to grow roses in the country.

He’d committed his fair share of sins (and more), and there are too many grey—and still more black—areas for Erdogan to turn into a benevolent pensioner overnight.

Especially when they still are—or feel—powerful.

It’s not because the grandiose displays he dreamt would showcase Turkish power on the world stage have done quite that, or because he has achieved the place he considers his by right in the international pecking order.

And his presence in the Middle East remains an open issue: disengaging from Israel unscathed won’t be easy, while re-engaging with Europe remains a pipe dream.

No, he did what he did because he has no guarantees that tomorrow will be as secure as yesterday. And Turkey is not a European democracy with unbreakable conventions and rules governing political culture.

Erdogan has proved that beyond any doubt as its ruler. And knows there’s nothing to stop his successor following that example.

So no one knows how this story—one which Erdogan himself would like to continue forever—will end. Clearly, though, he would like to secure or decide on his successor—or, better still, to succeed himself.

As the arrest of the mayor of Istanbul has shown, he’s already set his bid to do just that in motion.