The Democrats gathered at an Upper West Side election night watch party on Tuesday knew they had pulled off something big. Darializa Avila Chevalier, a democratic socialist running for Congress with the backing of Mayor Zohran Mamdani, had just unseated a five-term congressman.

It was a moment to celebrate progressive ideals, a sweep of congressional primaries by three candidates endorsed by the mayor. And for the many pro-Palestinian voters who backed Mr. Mamdani’s slate, it was a moment that seemed to validate the core ideals of their cause.

Ms. Avila Chevalier and the other two victorious House candidates — Brad Lander and Claire Valdez — backed by Mr. Mamdani are staunch critics of Israel’s treatment of Palestinians, and made their support for the Palestinian cause core to their campaign messages.

The magnitude of the primary results was especially striking to one well-known figure who was warmly greeted as he entered the watch party: Mahmoud Khalil, the Columbia University graduate student who organized pro-Palestinian demonstrations alongside Ms. Avila Chevalier, and became a symbol of the movement after his arrest and detention by the Trump administration for his activism.

Mr. Khalil said that the success of candidates like Ms. Avila Chevalier marked a meaningful step forward for the movement they helped lead.

“In the past, the question was: ‘OK, now we shifted public opinion on Palestine. What’s next?’” he said in an interview. “And I believe this is part of the ‘what’s next,’ which is converting the public support into real political power, whether on the local level or on the federal level.”

The wave of support for these pro-Palestinian candidates has altered a longstanding tradition among local leaders to support Israel in New York, home to the largest population of Jews outside of Israel. Some Jewish leaders have expressed alarm that the anti-Israel sentiment has fueled a rise of antisemitic attacks.

It is a remarkable shift from just a decade ago, when candidates who ran on an unabashedly pro-Palestinian platform were hushed down or deemed unviable in the face of a political status quo that demanded support for Israel.

Now, amid widespread discontent with establishment Democrats and eroding support for Israel among voters from both parties, a new crop of pro-Palestinian candidates who won state legislative or House primaries in New York has forged a new path for a movement that found its footing on college campuses and in the streets, rather than the halls of power. Their growing influence may help reshape how U.S. politicians approach the Middle East.

For Khader El-Yateem, a Palestinian Lutheran priest who ran unsuccessfully for City Council in 2017, the election results on Tuesday were something of a victory deferred. He ran on a campaign message that emphasized Palestinian rights and embraced the Boycott, Divestment and Sanctions movement against Israel. He lost by roughly seven percentage points.

“We ran on issues that meant something,” he said. “And I think people who are running for office are deeply committed to this nonviolence resistance of the Israeli occupation of Palestine.”

Aber Kawas, a Queens-based community organizer who spent years working in the city’s Arab and Muslim communities, won the Democratic primary for a State Senate seat on Tuesday. If she, as expected, wins in November, she will be the first Palestinian woman elected to state office in New York history.

“I didn’t want to see one more person enter into office, especially into a progressive district, where they wouldn’t speak out on this issue,” Ms. Kawas said, adding that it would be difficult for Democratic leaders to deliver an affordability agenda “if we can’t draw the line at genocide.”

Like Ms. Avila Chevalier, the two other pro-Palestinian congressional candidates who received Mr. Mamdani’s support have deep roots in the movement. Mr. Lander, the former city comptroller who ousted Representative Dan Goldman in the 10th District, is a self-described “liberal Zionist” who has been an outspoken opponent of Israel’s actions in the war in Gaza. And Ms. Valdez, a state assemblywoman, also supports the B.D.S. movement.

All three candidates have described the Israeli government’s actions in Gaza as genocide, in line with findings from Israeli and international human rights groups as well as two United Nations commissions. The two incumbents who lost, Representatives Adriano Espaillat and Mr. Goldman, had been supported by the American Israel Public Affairs Committee and disagree with the characterizations of Israel’s actions as a genocide. Mr. Goldman and Mr. Lander are both Jewish.

The influence of the movement itself was palpable throughout the campaign. Many of the volunteers and canvassers for pro-Palestinian candidates also participated in protests for Palestinian rights. At several victory parties on Tuesday night, including Ms. Avila Chevalier’s, chants of “Free Palestine!” could be heard amid cheers for the winning candidates.

Beth Miller, the political director of Jewish Voice for Peace Action, which supported Ms. Valdez and Ms. Avila Chevalier’s campaigns, said many of its members “who have been doing advocacy work to push our elected officials to try to get them to change — often with little results — have seen opportunities to get pro-Palestine champions who we know and who we have worked with over the years into office directly.”

Still, several of the candidates, should they win in November, will enter office with limited experience in electoral politics, setting up a test of their movement’s staying power at the legislative level.

Some of them will have to answer questions about their actions in support of the Palestinian cause. Ms. Avila Chevalier was widely criticized for going to a rally for Palestinian rights just a day after the Oct. 7 attacks by Hamas that killed 1,200 people, according to Israeli officials.

But Israel’s extended response to the attacks has, over time, caused alliances to shift, with more Americans now holding unfavorable views of Israel and the U.S. government’s support of the country.

According to the Pew Research Center, 60 percent of American adults and more than 80 percent of Democrats and Democratic-leaning independents hold an unfavorable view of Israel.

“The inclusion of Palestine in these conversations is a way of bringing parity to a discourse that has de facto been pro-Israel,” said Asad Dandia, a Brooklyn-based historian and ally of Mr. Mamdani. “And I think 10/7 and all of the events thereafter kind of accelerated the importance of bringing it to the forefront.”

There have also been noticeable shifts in how elected officials engage with Israel in recent years. Several elected officials, including Mr. Mamdani, declined to attend the Israel Day Parade in May, once a must-stop for the city’s politicians. Many of Mr. Mamdani’s predecessors in City Hall have also made official visits to Israel, but he has not signaled intent to travel there.

To longtime organizers for Palestinian rights, the string of political victories signaled that their movement to oppose Israel’s actions in Gaza and the West Bank is no longer fringe but a political force. Its growth also offers its most vocal supporters a broader platform to define their activism as a push for human rights and against war, and not antisemitism.

“The same volunteers who were knocking on the doors for Darializa and Claire were the same ones who were brutalized by the police, who their communities were targeted by ICE, who were expelled from their own universities and gaslit by their own politicians,” Mr. Khalil said. “The Palestine liberation movement in this country helped a lot in accelerating this change.”

And the pro-Israel lobby, once a lucrative ally to Democratic politicians supportive of Israel, has become an albatross of sorts for incumbents across the country. Both Ms. Avila Chevalier and Mr. Lander underlined the funding their incumbent opponents received from AIPAC in the past, even though the group spent sparingly in New York’s Democratic primaries during this cycle.

Allies of the pro-Palestinian movement see its growth as the start of a political realignment in the city that could reshape politics for a generation.

“For the first time, you have this movement that has the upper hand in the discourse,” Mr. Dandia, the historian, said. “And that’s going to cause some growing pains for a lot of people, but that’s just a part of, you know, democracy.”

Claire Fahy contributed reporting.