ATHENS, Greece (AP) -- Stefanos Kasselakis, a businessman who burst into Greek politics over a year ago, says he's leaving left-wing Syriza, the country's main opposition party he had led, and forming his own. Kasselakis announced he was leaving Syriza Friday after a two-day party congress refused to consider his leadership candidacy in a contest that will take place later this month. Kasselakis, 36, has lived most of his life in the U.S. and only entered Greek politics in May 2023 as a candidate in a national election. He unexpectedly entered the party leadership contest to replace longtime leader Alexis Tsipras and triumphed in September 2023.