Democratic leaders in Washington are facing increasing pressure to prod Israel to scale back military operations in Gaza, where rising civilian casualties have triggered human rights protests around the U.S. and sparked heightened calls for a cease-fire from Democratic lawmakers, administration officials and the party’s liberal base.

Behind President Biden, Democratic leaders have pressed for billions of dollars in humanitarian assistance for civilian victims of the conflict — Israeli and Palestinian alike. But they’ve rebuffed the entreaties of their left flank to back a cease-fire, citing Israel’s right to defend itself in the wake of Hamas’s brutal terrorist attacks on Oct. 7, which left roughly 1,200 people dead.

“Hamas has already said publicly that they plan on attacking Israel again,” Biden said Wednesday during a rare press conference in California. “And so the idea that they’re going to just stop and not do anything is not realistic.”

That position is growing more contentious as the civilian casualties continue to grow in Gaza, where more than 11,000 Palestinians — many of the children — have been killed since the war began, according to Gaza’s health ministry.

The rising toll has eroded public support for Israel’s handling of the conflict, according to recent polls, which is manifesting itself on a number of domestic fronts, all of which are creating political headaches for Democratic leaders.

In Boston, protestors this week blocked a well-trafficked bridge, in part to urge Sen. Elizabeth Warren (D-Mass.) to back a cease-fire. On Capitol Hill, Rep. Becca Balint (D-Vt.) on Thursday became the first Jewish lawmaker to support an immediate end to hostilities, reversing her initial position to join roughly two dozen of her House colleagues supporting a cease-fire. And hundreds of administration officials have reportedly written to Biden to protest his position on the conflict.

Some liberal activists, meanwhile, are warning Democrats of an electoral backlash in 2024 if they don’t endorse a cease-fire, saying the party’s continued support for Israel’s military operations will deflate the base to the advantage of former President Trump and Republicans.

“As someone who has personally worked to mobilize voters — particularly young voters — to vote for the Democratic Party in these elections, I know how crucial motivation and faith in the party is to being able to turn out people to vote,” Eva Borgwardt, the national spokesperson for IfNotNow, said Thursday. “And right now I know so many young voters, including Jewish voters, who are looking at the actions of our Democratic leadership and being completely, completely horrified and disillusioned by the response of our party to refuse to call for a cease-fire and end this horrific war.”

Borgwardt, who is Jewish, was among the activists who rallied Wednesday night at the Democratic National Committee’s (DNC) headquarters near the Capitol, where protestors challenged Democratic lawmakers to support a cease-fire — a demonstration that devolved into a violent altercation with U.S. Capitol Police, who evacuated lawmakers from the building.

The details of that clash are highly contested. The Capitol Police maintain that the protestors were violent, ignoring commands and pepper-spraying officers in an aggressive display that left six officers injured.

“We have handled hundreds of peaceful protests, but last night’s group was not peaceful,” the agency said.

The protestors deny those allegations, saying they were staging a peaceful candlelight vigil for victims of the conflict when the officers attacked them unprompted.

“That act of peace and moral act of civil disobedience was violently shut down by police who escalated against us and injured 90 of our community members,” said Jessica Rosenberg, a rabbi representing Jewish Voice for Peace. “The police officers gave no dispersal warning.”

A number of Democratic lawmakers who were at the DNC on Wednesday sided squarely with the Capitol Police, praising the officers on hand and denouncing the protestors for instigating the violence. The clash also forced House Democratic leaders to issue a statement Thursday, which condemned the protestors for “[escalating] their activity in a manner that exceeded a peaceful demonstration.”

“We strongly support the First Amendment right to freedom of expression and encourage anyone exercising that right to do so peacefully,” said the statement from Reps. Hakeem Jeffries (N.Y.), Katherine Clark (Mass.) and Pete Aguilar (Calif.).

The altercation was representative of the broader divisions within the Democratic Party when it comes to U.S. policy on Israel — differences only exacerbated by the Hamas attacks and Israel’s response — and emotions are getting more and more raw as the violence has entered its second month.

Those divisions cropped up in the recent vote to censure Rep. Rashida Tlaib (D-icisms of Israel — a measure supported by 22 pro-Israel Democrats. They’re surfacing in recent polls, which reveal that sympathy for Israel is waning as the conflict drags on, particularly among younger voters. They’ve been evinced by the efforts of pro-Israel Democrats, who have been scrambling to prevent any further erosion of support by highlighting the atrocities committed by Hamas against civilians, including children, on Oct. 7.

And they’re revealing themselves among liberal activists who are increasingly willing to confront their Democratic allies on the topic.

“Eighty percent of their base support a cease-fire and an end to the loss of life, [but] Democratic leadership and the Democratic Party is not aligned and is not listening to us,” said Dani Noble, an organizer with Jewish Voice for Peace Action.

The fiery debate is expected to continue in the weeks and months to come, as the number of casualties in the conflict rises each day, and as Congress is forced to revisit the thorny issue when lawmakers take up an emergency aid package upon their return to Washington after the long Thanksgiving break.

Biden has proposed a $105 billion supplemental funding package that earmarks $14.3 billion in aid to Israel, largely in the form of missile defense systems, and more than $9 billion for humanitarian assistance for civilians across several global hotspots, including Ukraine, Israel and Gaza.

Foreshadowing the coming conflict over that aid, Rep. Ilhan Omar (D-Minn.), one of three Muslims in Congress, introduced a resolution Thursday to block the sale of certain U.S. weapons to Israel.