Recep Tayyip Erdogan, Turkey's president, waves to supporters during a 'Yes' referendum campaign rally in Umraniye, Istanbul, Turkey, on Saturday, April 15, 2017. Turkish voters will decide on Sunday whether to endorse president Erdogan's bid to centralize power in his hands in the most radical shake-up since the republic was formed 93 years ago. Photographer: Kostas Tsironis/Bloomberg via Getty Images