A Watershed Moment for the Politics of Israel, Courtesy of Chuck Schumer

Over 44 painstakingly scripted minutes on the floor of the Senate on Thursday, the majority leader, Chuck Schumer, spoke of his Jewish identity, his love for the State of Israel, his horror at the wanton slaughter of Israelis on Oct. 7 and his views on the apportionment of blame for the carnage in Gaza, saying that it first and foremost lay with the terrorists of Hamas.

Then Mr. Schumer, a New York Democrat and the highest-ranking elected Jew in American history, said Israel’s prime minister, Benjamin Netanyahu, was an impediment to peace, and called for new elections in the world’s only Jewish state.

The opposition was not nearly so painstaking.

Within minutes, the House Republican leadership demanded an apology. The Senate Republican leader, Mitch McConnell of Kentucky, using Mr. Netanyahu’s nickname, declared: “Make no mistake — the Democratic Party doesn’t have an anti-Bibi problem. It has an anti-Israel problem.” And the Republican Jewish Coalition proclaimed that “the most powerful Democrat in Congress knifed the Jewish state in the back.”

The months that have followed the slaughter of Oct. 7 and the ensuing, calamitously deadly war in Gaza have been excruciating for American Jews, caught between a tradition of liberalism that has dominated much of Jewish politics and an anti-Israel response from the political left that has left many feeling isolated and, at times, persecuted.

But Mr. Schumer’s speech was potentially a watershed moment in a much longer political process, pursued initially by Republicans but joined recently by left-wing Democrats — to turn Israel into a partisan issue. Republicans, as they see it, would be the party of Israeli supporters. Democrats, as the rising left would have it, would be the party of Palestine.

At the root of that divide is a fundamental question: Is support for the Jewish State separable from the support of Israel’s democratically elected government? For years, Republicans have said no. Increasingly, the Democratic left agrees but from a different perspective: Israel is bad, regardless of who governs it.

“The pressure — electoral, social, cultural — on American Jews right now to declare themselves” on the justice of the war in Gaza and on the legitimacy of the Israeli prime minister has been “unrelenting, unforgiving and sometimes downright vicious,” said David Wolpe, a prominent rabbi in Los Angeles and a visiting scholar at Harvard Divinity School.

Mr. Schumer’s speech and the ensuing partisan response have made that pressure even more intense.

“It’s impossible to understate the seismic event this was,” said Matthew Brooks, the longtime chief executive of the Republican Jewish Coalition, who made it clear that the group would use the speech to drive Jewish voters to the G.O.P.

While Republicans accused Mr. Schumer of trying to force an election at a time when most Israelis support and are focused on the war against Hamas, the Senate leader was, in fact, cognizant of Israeli public opinion. He noted that “so many Israelis have lost their confidence in the vision and direction of their government,” a phrase backed up by polling that indicates Mr. Netanyahu is deeply unpopular. Mr. Schumer was also careful to say that elections should be called only “once the war starts to wind down” and that he would respect their outcome.

Jewish Democrats have long maintained that support for a Jewish state in the traditional homeland of the Jewish people is intrinsic to their identity, regardless of the government in power in Jerusalem. Mr. Schumer tried to make that point from the outset of Thursday’s speech, explaining that his last name derived from the Hebrew word for “guardian.” He is, he said, a “shomer Yisrael — a guardian of the people of Israel.”

But his speech came at an incendiary moment, when support is eroding among Democrats for what Senator Bernie Sanders, independent of Vermont, calls “Netanyahu’s war,” and loud voices on the left are saying that the state of Israel is intrinsically wrong: a “settler colonialist” intruder incompatible with the rights and sovereignty of the Palestinian people who lived there before Israeli independence in 1948.

“You have this divide where the overwhelming majority of American Jews support Israel, support its right to exist as a Jewish state, and an increasingly vocal minority doesn’t support Israel as a Jewish state and rejects what happened in 1948 to ensure that the Jewish state survived,” Michael J. Koplow, chief policy officer of the Israel Policy Forum, a Washington-based research group, said on Friday from Israel.

He continued: “Schumer needed to preserve some way to criticize the Israeli government without being even close to Camp No. 2, which is why he spent so much time at the beginning talking about Hamas’s culpability and his love of Israel.”

But at such a political moment, any notion of “nuance” — a word Mr. Schumer used when he lamented the “silent majority” of Jews whose “nuanced views have never been represented in discussions about the war in Gaza” — most likely did not sink in.

Republicans made no secret that they would use Mr. Schumer’s words against him. The National Republican Senatorial Committee blasted out emails demanding that vulnerable Democrats up for re-election this year speak out against Mr. Schumer’s views.

Norm Coleman, a former Republican senator from Minnesota who went to public school with Mr. Schumer in New York and now chairs the Republican Jewish Coalition, said on Friday that whatever bipartisanship remained around support for Israel might have been obliterated by Mr. Schumer’s denunciation of Mr. Netanyahu and his call for new elections. He accused Mr. Schumer of political motives driven specifically by President Biden’s travails with Arab Americans in the pivotal swing state of Michigan.

“I don’t think Schumer is speaking for American Jews,” Mr. Coleman said. “I think he’s speaking as the majority leader of a Democratic Party now so worried about the left, so worried about Michigan, that he gives a speech telling the democratically elected government of a democratic country that they shouldn’t be the government anymore.”

Even some centrist Jewish Democrats, such as Representative Brad Schneider of Illinois, condemned Mr. Schumer’s call for new elections in Israel as meddling in the affairs of what he called “the only true democracy in the region.”

For many older liberal Jews, however, Mr. Schumer’s words were a tonic. They were an articulation of their shared agonies over the deaths of tens of thousands of Palestinians in Gaza, and their frustrations with an Israeli government that includes far-right ministers, whom Mr. Schumer called out by name, who adamantly oppose any concessions for peace or Palestinian sovereignty. His words were also an expression of the Democrats’ rising desire to use what Mr. Schumer called “leverage” tied to billions of American tax dollars flowing to the Israeli military.

Daniel G. Zemel, a Reform rabbi in Washington, D.C., and an advocate of “liberal Zionism,” said Mr. Schumer’s prescriptions were “exactly what American Jews should be calling for.”

“There has to be a different approach,” he said, pushing back on those who called Mr. Schumer’s prescriptions anti-democratic. “As a rabbi and as a Jew, I have a right and an obligation to say what I want Israel to be in this world.”

Representative Jerrold Nadler, Democrat of New York and the dean of the Jewish House members, posted on social media that Mr. Schumer “is right,” adding, “Prime Minister Netanyahu has become an obstacle to peace and the two state solution.”

Representative Jan Schakowsky of Illinois is one of those progressive Jewish Democrats who feel caught in a vise between activists harassing her as “Genocide Jan” and her personal conviction that Israel has a right to exist as a Jewish state, side by side with a sovereign Palestinian state. It is, she acknowledged, a “fraught moment” for politicians like herself, but she said on Friday that Mr. Schumer was speaking for a majority of Jews in the United States and Israel.

She hotly dismissed the notion that Mr. Schumer was intruding on Israeli democracy, noting that Mr. Netanyahu spoke in 2015 to Congress to pressure President Barack Obama to abandon his nuclear accord with Iran.

“There is a hunger right now for another path, and that is what Schumer had the courage to talk about,” she said. “Most Israelis and American Jews understand the importance and the essential role the United States plays, and we feel like Bibi is thumbing his nose at us.”