For the Democratic Party, where most Jews have long made their political home, the risks are clear — and visible across the Atlantic. In Europe, left-wing parties are courting Muslim immigrant voters with increasingly anti-Israel positions, while the populist right is wooing Jews and cozying up to Israel’s right-wing government. In Britain, the leader of the Labour Party is besieged by accusations of anti-Semitism, bringing British Jews to the streets of London in protest.

Mr. Trump and Republicans are trying to find the same rifts among Democrats. Next week, the Senate is expected to easily pass legislation aimed at curbing the boycott-Israel movement — and stifling the new Democratic voices like Ms. Tlaib and Ms. Omar that back it. The bill would allow state and local governments to break ties with companies that participate in the Boycott, Divestment, Sanctions, or B.D.S., movement, which is intended, among other things, to pressure Israel into ending the occupation of the West Bank, and backed by some who advocate a single state with equal rights for all, instead of a Palestinian state alongside Israel.

Backers of B.D.S., including Ms. Tlaib and Ms. Omar, argue that economic boycotts are protected by the constitutional right to free speech; opponents insist the movement’s true goal is to destroy Israel as a Jewish state. The Senate bill, which has considerable Democratic support, is destined to fail in the House, where Representative Hakeem Jeffries, the Democratic Caucus chairman, has labeled it a “political stunt.”

But the debate is more than political. It is also playing out at the uncomfortable intersection of race, gender and religion in a Capitol whose complexion has changed dramatically with the arrival of an extraordinarily diverse freshman class. Allies of Ms. Tlaib and Ms. Omar accuse Republicans of bullying and bigotry, and they say Republicans are looking for a Democratic twin of Mr. King, the Iowa Republican who was recently rebuked by the House for his seeming embrace of white supremacy.

“I see this as an Islamaphobic attack against two outspoken women of color who are shaking things up by boldly standing for crucial issues,” said Yousef Munayyer, executive director of the U.S. Campaign for Palestinian Rights. Critics of Ms. Tlaib and Ms. Omar, he said, are failing to recognize that “Palestine is increasingly becoming part of the progressive politics of justice for all.”

