Brad Lander, an ally of Mayor Zohran Mamdani, won the Democratic primary in a progressive New York House district on Tuesday, according to The Associated Press, in a race that hinged largely on the candidates’ different stances on the Israeli-Palestinian conflict.

With 53 percent of the vote counted, Mr. Lander, a former city comptroller and mayoral candidate who has criticized Israel’s war in Gaza, was almost 30 points ahead of the incumbent, Representative Dan Goldman, a pro-Israel former federal prosecutor who helped lead the first impeachment inquiry into President Trump.

Mr. Lander benefited from his deep roots in the 10th District, which covers Lower Manhattan and parts of Brooklyn. His victory makes him the likely winner of the general election in November.

Mr. Lander, 56, was one of three progressive primary candidates endorsed by Mr. Mamdani, with whom he has had a political alliance since last year’s Democratic mayoral primary.

The two men began as rivals, but cross-endorsed each other as the primary date closed in, saying they wanted to work together to keep former Gov. Andrew M. Cuomo from winning the nomination. Their alliance has elevated them both — Mr. Mamdani to City Hall, and Mr. Lander to the cusp of a congressional victory.

Mr. Lander reflected on the decision to team up with Mr. Mamdani during a televised debate last week, saying it had modeled a new kind of politics for New York.

“It unleashed a nice sense of solidarity,” he said on the debate stage. “People said to me, ‘Wait, you mean politics doesn’t have to be a sour, selfish ego trip — it can be a team sport for the values you share?’”

Among several closely watched primaries across the city and state, the contest in the 10th District was notable for the degree to which it was dominated by the Israeli-Palestinian conflict. Both Mr. Lander and Mr. Goldman are Jewish and describe themselves as liberal Zionists, but they approach the issue in very different ways.

Mr. Lander has spent decades in the world of progressive Jewish activism, working with organizations like Jews for Racial and Economic Justice and cofounding the New York Jewish Agenda, a left-leaning group.

He has also been a longtime player in Democratic politics in New York City, and entered the primary with a committed base and a groundswell of good will in the district.

He spent many years running a community development organization in Park Slope, then served on the City Council for more than a decade representing several of the congressional district’s neighborhoods. After he left the Council, he served as city comptroller, during which time he chose not to repurchase State of Israel bonds that had matured.

Mr. Lander has been an outspoken critic of Israel since the start of the war in Gaza, which began after the Hamas-led terror attack on Oct. 7, 2023.

Mr. Lander has backed claims by human rights groups and a United Nations commission that Israel has committed genocide in Gaza, frequently using that word on the campaign trail, and has said he supports legislation to block U.S. military aid to the country until it meets human rights standards.

Mr. Goldman’s views hew more closely to the longtime status quo in American politics regarding the U.S.-Israel relationship. He is a critic of Israel’s prime minister, Benjamin Netanyahu, but has said he supports continuing to provide the military aid that underpins the decades-long alliance between the two countries.

And he has said he does not believe Israel has committed genocide in Gaza or that its treatment of the Palestinians can fairly be described as apartheid — another word Mr. Lander frequently uses — calling them ideologically charged terms.

Mr. Goldman accepted the endorsement of the American Israel Public Affairs Committee, a hard-line pro-Israel lobbying group increasingly shunned by Democrats, but was also endorsed by J Street, a more liberal pro-Israel group.