In her Twitter statement on Monday, Ms. Omar did not back away from her contention that Aipac has too much power in Washington. “At the same time, I reaffirm the problematic role of lobbyists in our politics, whether it be Aipac, the N.R.A. or the fossil fuel industry,” Ms. Omar wrote.

Critics of Israel say Ms. Omar has a point. In separate interviews on Monday, both Emily Mayer, the national coordinator of IfNotNow, a liberal Jewish group, and Yousef Munayyer, the director of the U.S. Campaign for Palestinian Rights, said Ms. Omar was forcing an important discussion in Washington.

“Twitter is probably not the best medium for nuanced conversation,” Mr. Munayyer said. “But I don’t think the correct answer is we can’t talk about it. I think it is very important in this moment to have a conversation about U.S. relations with Israel.”

Ms. Mayer said she “wholeheartedly” accepts Ms. Omar’s “apology for her word choice while also appreciating the moral stance that she takes on this issue, which is pretty unprecedented in today’s Congress.”

Monday’s back and forth came on top of earlier flash points that pitted Ms. Omar against Israel’s fiercest supporters in Congress, Republican and Democrat. She told Yahoo News last month that when politicians “still uphold” Israel “as a democracy in the Middle East, I almost chuckle.” That brought back criticism of a 2012 tweet in which she accused Israel of hypnotizing the world to mask its evil deeds.

She had been trying to mend fences over those comments when Sunday night’s tweet went viral.

Before the leaders’ statement on Monday, other Democrats had broken rank to voice their condemnations. Two House Democrats, Representatives Elaine Luria, a freshman from Virginia, and Josh Gottheimer of New Jersey, released a letter Monday morning calling on Democratic leaders to speak out against any lawmaker who “uses harmful tropes and stereotypes, levels accusations of dual loyalty or makes reckless statements like those yesterday.”

“As Jewish members of Congress, we are deeply alarmed by recent rhetoric from certain members within our caucus, including just last night, that has disparaged us and called into question our loyalty to our nation,” they wrote. “We urge you to join us in calling on each member of our caucus to unite against anti-Semitism and hateful tropes and stereotypes.”

