When George Santos, the indicted fabulist, was expelled from Congress in December, Nassau County Republicans scrambled to hunt up a new nominee. Santos was a catastrophe, but he had also flipped a New York Democratic stronghold, and party leaders wanted the best of him — the charisma, the conservatism and the history-making potential — with none of the debilitating drawbacks.

There had been chatter about a Nassau County legislator who, in the wake of the Oct. 7 Hamas terrorist attack on Israel, moved some listeners at a local Jewish Community Center to tears. Mazi Pilip, an Ethiopian-born Israeli American, recounted how her family members had huddled together in a bomb shelter. She told one sister that she wanted to put on, once more, the uniform of the Israeli military. “I had a hope, a little hope, one day there will be a peace,” she recalled, her voice cracking. “I have so many family members, right now, fighting.”

The speech alone most likely did not persuade Republicans to nominate Pilip in the Feb. 13 special election to replace Santos. But it may have been decisive. They needed someone who could go up against Tom Suozzi, the veteran Democrat who gave up the seat to run unsuccessfully for governor in 2022 and was now running again. Pilip, despite her avowed conservatism, has been a longtime registered Democrat; she seemed the perfect candidate to help Republicans aggressively court a Jewish community that once backed Democrats and was now, in the anguished weeks after Oct. 7, debating whether the party should represent them again.

“The lefty progressive Democrats, they do not support Israel,” Pilip told me. “It’s shameful. When I go to Congress, they’ll face a Black woman, a mother of seven children, a former I.D.F., a proud American. They’re going to face me.”

Pilip’s candidacy is emblematic of a remarkably volatile moment in American politics. Since Hamas killed around 1,200 people and took about 240 hostages, and Israel retaliated by shelling Gaza, leaving more than 26,000 dead, there has been a sense within the Democratic Party of a divide that cannot be bridged, an eruption of ill feeling that will not dissipate.