NEW YORK — Just as Democrats are finding their footing by focusing on affordability, their differences on Israel are threatening to tear them apart.

Spurred by polling that shows support for the Jewish state slipping among voters nationally, congressional challengers are lining up across the country to take on stalwart Israel supporters in an attempt to energize left-leaning voters. But the deluge of Democratic primaries being waged in some part over this issue also threatens to exhaust resources, muddy the party’s messaging and bloody candidates ahead of the general election.

Pro-Israel Democrats believe supporters should mobilize with urgency to confront this crop of challengers.

“The main, centrist Democratic Party as a whole is doing a terrible job managing this whole process,” said Mark Botnick, a former advisor to ex-New York City Mayor Michael Bloomberg, who contributed more than $10 million to efforts opposing Zohran Mamdani’s successful mayoral campaign. “That’s not to say the Israeli government has made it easy for them. It’s fine for someone to be against their policies, but it’s very different to be against the existence of the Jewish state, which in my eyes is antisemitism. The party has done an abysmal job of getting up and saying that.”

Next year’s midterms are pivotal: Democrats locked out of power in Washington need only net three House seats and four in the Senate — a tougher task — in order to seize control over either chamber.

Pro-Israel incumbents are facing challenges in New Jersey and New York, while primary battles in Michigan and Illinois are also being prepped by pro-Palestinian candidates. The coming contests have put Democrats on edge. As they try to win back power in the closely divided House, they are desperate to avoid messy primary races.

The American Israel Public Affairs Committee is mobilizing too — months before the first vote is cast — to identify potential incumbents who need shoring up as the primary fields take shape.

“Our 6 million grassroots members understand the stakes in the upcoming midterms, and that is why they are deeply motivated and engaged to help elect pro-Israel candidates and defeat detractors,” said AIPAC spokesperson Marshall Wittmann.

The Democratic Majority For Israel’s political action committee got an early jump on the cycle as well — so far endorsing 26 Democratic House incumbents across the country, an initial slate that includes lawmakers in Illinois, California, Pennsylvania and Ohio. The group’s board chair, Brian Romick, called it a “critical moment for the U.S.-Israel relationship.”

Primary bids fueled by opposition to Israel are complicating Democrats’ path to victory next year, despite signs of increasingly favorable political terrain following wins in Georgia, Virginia and New Jersey. The efforts underscore the yawning chasm facing Democrats over Israel more than two years since the Oct. 7 attacks by Hamas and a devastating war in Gaza that has killed thousands of Palestinians. Jewish Democrats are alarmed by what they consider open antisemitism among far-left candidates encouraged by Mamdani’s success in the New York City mayoral race.

AIPAC-backed Rep. Rob Menendez in New Jersey appears likely to draw a challenge from Mussab Ali, a former local school board president with a strong social media following. Ali, like Mamdani, began criticizing Israel within weeks of the Oct. 7 attacks — early compared to most people with hopes of running for office.

Michigan’s open Democratic Senate primary offers another microcosm of the party’s evolving dynamics on the issue. The three-way brawl pits a sitting representative backed by the pro-Israel lobby against a former booster of the “uncommitted” movement to pressure a Gaza ceasefire and a progressive state lawmaker who’s shifted away from Israel.

The Middle East crisis is also reshaping the contours of at least two House Democratic primaries in Illinois — home to large Jewish, Middle Eastern and Muslim communities. Statewide the tensions are apparent as well in the U.S. Senate contest to replace retiring Democrat Dick Durbin.

And in New York City, home to the nation’s largest Jewish population, left-leaning challengers backed by the Democratic Socialists of America are eager to unseat Israel-supporting incumbent Reps. Dan Goldman, Grace Meng, Ritchie Torres and Adriano Espaillat.

That includes a Mamdani-endorsed challenge to Goldman by former New York City Comptroller Brad Lander — a primary that promises to be a marquee intraparty fight over the issue.

If successful, candidates willing to criticize Israel stand to remake a Democratic Party that has historically backed the Jewish state since its 1948 founding — a path some party officials acknowledge already may be too difficult to alter after the war isolated the country. The challenges by Israel critics, too, highlight growing Muslim populations and commensurate political strength in pockets around the country.

Foreign affairs has divided Democrats before. Opposition to the war in Iraq helped Barack Obama stand out as a state senator in Illinois, while higher-profile pro-war Democrats — like Hillary Clinton — saw their electoral fortunes sink when support for the war became a disqualifying issue among Democrats.

Israel — and increasing hostility from the left toward it — has conjured deep-seated emotions among Democrats watching the situation unfold with disbelief. Taken together, there’s a pervasive worry among Jewish political leaders that shifting political winds in the United States will have long-term consequences for Israel — and Jews — in the decades to come.

“The whole democratic socialist movement has become very anti-Israel, which I don’t understand at all,” said David Weprin, a Queens state lawmaker. “I grew up with Israel being a very progressive country, a democratic country, one that tolerates everyone. It’s definitely something that I find disturbing.”

Democrats’ divisions over Gaza are perhaps nowhere more pronounced than in Michigan, where disparate views of Israel continue to roil state politics and where Democrats are grappling with how to re-engage Arab American voters who shifted toward Trump last year.

In Michigan’s marquee Democratic Senate primary, DMFI PAC endorsed Rep. Haley Stevens, who’s viewed as the establishment pick and who represents a substantial Jewish population. Stevens described herself as a “proud pro-Israel Democrat” in accepting DMFI’s support. She also said she’d fight in the Senate to “support Israel’s security [and] ensure the ceasefire holds in Gaza.” AIPAC’s PAC, which has funneled millions toward Stevens in the past, has yet to issue an endorsement this cycle but features her prominently on its website.

Her opponents have taken far more critical stances toward Israel.

Abdul El-Sayed, a past gubernatorial hopeful who backed the “uncommitted” movement during the 2024 presidential primary but later endorsed Vice President Kamala Harris, has described Gaza as a Rorschach test for Democrats’ values. He has repeatedly criticized Israel’s military actions and the U.S. dollars funding them — and has used those stances to draw contrasts with rivals.

El-Sayed was the first in the race to call the conflict in Gaza a genocide, a stance state Sen. Mallory McMorrow later adopted. McMorrow also joined El-Sayed in rejecting support from AIPAC. And both said they would have voted in favor of resolutions from Sen. Bernie Sanders blocking weapons sales to Israel — legislation Stevens said she would have voted against.

McMorrow, whose husband is Jewish and whose daughter was the target of death threats after the Oct. 7 attacks, has shifted on Israel in a way that reflects the broader transformation occurring within the Democratic Party. She initially declined to call the war a genocide, but changed her stance in October after a September United Nations report claiming Israel had committed one.

El-Sayed has indirectly criticized McMorrow for being a late adopter of his positions as the two progressives compete for the same slice of voters, including younger voters for whom Gaza remains an animating issue.

The primary will also provide an early test of whether Michigan Democrats have been able to reengage Muslim voters, like those in Dearborn who have historically backed Democrats but who split their tickets last year between Trump and Democratic Sen. Elissa Slotkin.

“The politics around Israel-Palestine have changed dramatically over the last few years,” said a Democratic strategist who’s worked on Michigan races and was granted anonymity to speak candidly about the Senate primary’s dynamics. “For 2026 and beyond, it’s less about candidates reacting and more about what they believe on the issue as a matter of core values. Just claiming to support a two-state solution isn’t going to cut it anymore.”

Tensions over Israel are also simmering in a pair of Illinois House races and the U.S. Senate contest.

The House seats are currently held by Rep. Jan Schakowsky, who is retiring, and Rep. Raja Krishnamoorthi, who is running for the U.S. Senate seat now held by Durbin.

State Sen. Laura Fine, one of the top candidates vying for Schakowsky’s seat, has been the beneficiary of a supportive AIPAC email — even though the organization has yet to endorse or donate to her campaign directly. Other high-profile candidates among the 17 in the Democratic primary include the left-leaning suburban Mayor Daniel Biss and social media influencer Kat Abughazaleh. Biss is Jewish, and Abughazaleh is Palestinian-American.

The district spans Chicago and Evanston — home to Northwestern University — and includes suburban communities with significant Jewish, Muslim and Arab populations.

In the district now held by Krishnamoorthi, candidates Junaid Ahmed and Yasmeen Bankole have both made Gaza a campaign priority and are running against former Rep. Melissa Bean, who hasn’t been endorsed by AIPAC but is viewed as a more moderate candidate.

In New Jersey, Menendez appears to be hedging in a district that has significant Arab and Jewish populations. While he supports Israel, he has also chastised colleagues for Islamophobia, including “vile rhetoric” directed at Mamdani.

“My record of delivering for all of our residents and standing up to the Trump Administration speaks for itself. The same is true for my approach to the Middle East, from advocating for the release of the hostages, to surging humanitarian aid to Gaza, to working towards a lasting and durable peace for the region,” he said in a text message. “I look forward to having that conversation and will forcefully push back on any attempt to misrepresent my record.”

As support for Israel has weakened, Menendez’s likely challenger Ali believes pro-Israel politics can be disqualifying for incumbent Democrats.

“Eventually, politicians who think that they can hide behind talking points will be outed,” Ali said. “You’re seeing that right now with a bunch of people challenging AIPAC’s influence.”

Mamdani’s meteoric rise has fueled far-left challenges to incumbent Democrats across the Big Apple. Several Democrats have expressed interest in running against pro-Israel Democrat Dan Goldman. In the Bronx, former Democratic Committee Vice Chair Michael Blake has predicated his campaign on running against Torres’ stridently pro-Israel views.

The dynamic facing the party is a reversal from the 2024 cycle, when moderate Democrats backed by millions of dollars in support from AIPAC ran to oust anti-Israel lawmakers. The Democratic Majority for Israel PAC spent more than $11 million on races across the country during the 2024 election as well, with 80 percent of its endorsed candidates winning their races.

In New York City’s suburbs, Rep. George Latimer successfully defeated incumbent Democrat Jamaal Bowman after a bitterly fought race featuring plenty of rhetoric about Israel.

Latimer, who was among the incumbents recently endorsed by DMFI, said in an interview he expects another left-flank primary challenge next year, driven in part by opposition to Israel. Prominent Jewish leaders in New York, though, are skeptical the posture makes much sense when most voters are focused on pocketbook concerns — an issue effectively leveraged by Mamdani.

“Everybody in America wants to be Zohran Mamdani, but there’s only one Zohran Mamdani,” said David Greenfield, a former city councilmember and head of The Met Council, a Jewish charity. “The reason he won is not because of Israel, he won because of affordability.”