ATHENS, Greece (AP) — Greece’s main opposition party suffered a split Sunday when a left-wing faction announced it was breaking away, accusing the party’s recently elected leader of abandoning its core ideology for a sort of “right-wing populism.”

Umbrella, a faction led by Euclid Tsakalotos, a former Finance Minister during Syriza’s government of 2015-19, announced its departure with a blistering statement that accused party leader Stefanos Kasselakis of “Trumpian practices (and) right-leaning populism.”

The once-dominant party has been in disarray ever since its resounding defeat by conservative New Democracy in double elections in May and June.

Already in opposition since 2019, Syriza had hoped to regain power. Instead, it was roundly disavowed, falling in the most recent election to 17.8%, compared to New Democracy’s 40.6%, a result that led longtime leader Alexis Tsipras to announce his resignation.

The split, which came after weeks of withering criticism of the leader from within the party, became inevitable in recent days, when Kasselakis insisted he wanted to expel three prominent members of the Umbrella faction, all former ministers.

When it became clear he might not get his way with party organs, Kasselakis said he would put the question to a referendum among party members.

This proposal drew a rebuke even among his allies. In a tumultuous session of the party’s Central Committee Saturday, Kasselakis’ confrontational speech was often interrupted with boos and shouts of “shame!” Umbrella, as well as supporters of Effie Achtsioglou, Kasselakis’ main rival in last September’s leadership election, left before the session was over.

Kasselakis won the leadership election that followed Syriza’s defeat at the polls in September. A political neophyte and US resident, with no connection to the party before he became a candidate for the May election, he came out of nowhere to win the contest. A four-minute video in which he told his life story shot him to prominence and made him the favorite.

Kasselakis’ style, based on social media presence and charisma, and his past as a former Goldman Sachs employee and shipowner, rankled with old-school leftists, who were also incensed with some of his positions, such as advocating stock options for employees, and his overall ideological vagueness.

They openly derided him for his “post-politics” and one prominent party person even compared him with former US President Donald Trump and Italian comedian Bepe Grillo, founder of a populist political party.

The new leader’s supporters, in turn, accused their rivals of having conspired to undermine former leader Tsipras in the run-up to the disastrous elections and even for years before. The current opinion polls, which show Syriza in a tight race for second place with the socialist Pasok party, intensified the malaise within Syriza.

Although the Umbrella supporters have not clarified their future plans, they are expected to form a new left-wing political party. They also have the backing of most of Syriza’s youth wing.

Achtsioglou, who leads her own faction, called 6+6, has decided to stay in Syriza, but her own relations with her leader are poisoned. She and her group issued their own statement Sunday, after the left’s departure, slamming Kasselakis’ “deeply offensive and divisive speech” and accusing him of using the vocabulary of the alt-right.

A further split of the party cannot be ruled out.