Representative Daniel Goldman of New York City has pledged at least $1 million of his personal fortune to defend his House seat and will match every donation he receives ahead of the June primary. The move comes as he faces a strong challenge from Brad Lander, a former city comptroller, in the 10th Congressional District. Private polling shared with allies shows Mr. Lander holding a significant lead.

Mr. Goldman, an heir to the Levi Strauss fortune and one of the wealthiest members of Congress, said he decided to self-fund after what he described as misleading attacks about his record and accusations that he is influenced by special interests, including the American Israel Public Affairs Committee. He said matching donations would demonstrate that he is guided only by his voters and his principles.

Mr. Lander criticized the decision, accusing Mr. Goldman of trying to buy the election, and urged his own supporters to increase their contributions. The race has highlighted divisions within the district’s Democratic base, particularly over Israel’s war in Gaza and the direction of local progressive politics.

While Mr. Goldman has generally supported military aid to Israel, he has recently sought to distance himself from broader Middle East conflicts, releasing a new advertisement opposing American and Israeli military action in Iran. The increasingly expensive and combative primary underscores the shifting political landscape in a safely Democratic district that is no longer guaranteed territory for an incumbent.