A young progressive Democrat who has sharply criticized Israel, including calling the killing of Palestinian protesters on the Gaza border in May a “massacre,” celebrated an upset victory over a leading House Democrat in a congressional primary race in New York City on Tuesday.

Alexandria Ocasio-Cortez, 28, scored a decisive win over powerful congressman Rep. Joe Crowley, 56. Many observers had believed he was a strong candidate to succeed Rep. Nancy Pelosi as speaker of the House of Representatives.

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Riding a wave of strong anti-Trump “resistance” sentiment in her New York district, Ocasio-Cortez – who belongs to the Democratic Socialists of America and is a supporter of Bernie Sanders – ran on a far-left platform. Her agenda included Medicare-for-all and clamping down on Wall Street.

Open gallery view A sign for progressive challenger Alexandria Ocasio-Cortez at her victory party in the Bronx after an upset against incumbent Democratic Representative Joe Crowley in New York City on June 26, 2018. Credit: Scott Heins/AFP

Her victory is being seen as a bellwether for a Democratic Party that is shifting to the left and including more women and people of color as candidates. Crowley’s defeat is seen as a warning to other establishment Democrats.

Her victory Tuesday virtually assures Ocasio-Cortez a seat in Congress, given that New York’s 14th District, which incorporates parts of both Queens and the Bronx, is overwhelmingly Democrat.

In the midst of her primary campaign, Ocasio-Cortez spoke out strongly against the Israeli army’s actions on the Gaza border on May 14, tweeting, “This is a massacre. I hope my peers have the moral courage to call it such. No state or entity is absolved of mass shootings of protesters. There is no justification. Palestinian people deserve basic human dignity, as anyone else. Democrats can’t be silent about this anymore.”

Asked later why she chose to post the tweet, Ocasio-Cortez compared the Gaza protesters to civil rights activists in the United States.

“I think I was primarily compelled on moral grounds because I could only imagine if 60 people were shot and killed in Ferguson. Or if 60 people were shot and killed in the West Virginia teachers’ strikes. The idea that we are not supposed to talk about people dying when they are engaging in political expression just really moved me,” she said.

She told interviewer Glenn Greenwald that the “silence” around the Palestinian cause “has been a little interesting to me,” adding that her Puerto Rican roots her to relate to the Palestinian protesters.

“Puerto Rico is a colony that is granted no rights, that has no civic representation,” she said. “If 60 of us were shot in protest of the U.S. negligence in FEMA I couldn’t imagine if there were silence on that.”

Increasingly, she said, “People are separating the actions and status of Palestinians from even the greater geopolitics of the area. People are looking at Palestinians through a humanitarian lens.”

Crowley had been in Congress since 1999 and was the number four Democrat in the House. He was known to have strong links to Wall Street and had reportedly crowdfunded nearly $3 million in his battle for the 14th District seat. However, he had been criticized for ducking several primary debates with his rivals, leading to a stinging rebuke from a New York Times editorial.