Well over a year into Donald Trump’s disruptive second term, few believed the US president could still genuinely shock. But at 8.06am on Tuesday he did just that, with an apocalyptic threat on Truth Social, to destroy a “whole civilization” in Iran – a country of more than 90 million people. Democrats abandoned their forced restraint and immediately began to call for Trump’s removal from office.

Yet beneath Democrats’ near-universal opposition to what they call the president’s “war of choice” are simmering tensions about the way America should engage with the world, especially when it comes to the Middle East. Since losing to Trump and his America First agenda in 2024, which promised not to start new wars, leading progressives have urged Democrats to reclaim the “anti-war” mantle.

“Voters, especially young people and working families, are exhausted by ‘forever wars’,” said Naveed Shah, an Army veteran and a political director at the progressive veterans advocacy groups Common Defense.

Now that Trump has opened a new chapter of US-led warfare in the Middle East, these voices on the left are growing louder and more emboldened, sensing a rare opportunity to reorient American foreign policy around a working-class worldview.

“The party has to stand for something bigger than ‘not Trump’,” Shah said, “and at this moment that is a foreign policy that demands accountability.”

Across the party, elected officials, candidates and activists are grappling with what the US and Israeli-led assault on Iran says about American power and its moral standing in the world. The internal debate comes as Democrats try to rebuild after 2024, in light of findings that the Biden administration’s approach toward Israel’s war on Gaza cost Democrats critical support in the last presidential election.

Matt Duss, executive vice-president of the Center for International Policy and a former top foreign policy aide to Senator Bernie Sanders, said the current conflict has “clarified for much of the Democratic party that the left is correct about foreign policy”.

He called the Iran war “another expression of Trump’s authoritarianism” and warned against a “Republican lite” approach to foreign policy embraced by Democrats who believe the answer to Trump’s aggression is to find a “nicer way” of “doing global hegemony”.

“We really need to break away from militarism,” Duss said. “We need to slash the defense budget. We need to invest domestically. That doesn’t mean we withdraw from the world, but we don’t engage in the world primarily through the military tool.”

Though Trump ultimately backed off his most dire threat, forging a shaky ceasefire shortly before his self-imposed Tuesday night deadline, Congressional Democrats are once again under pressure to use the few tools at their disposal to rein in the president.

This week, they came out by the dozen to call for Trump’s removal from office, as constituents flooded congressional phonelines with calls about Iran. Any attempt to impeach Trump while Republicans control Congress is doomed to fail, and some Democratic leaders and moderates fear a focus on impeachment will distract from their economic message.

Speaking to reporters on Capitol Hill after Republicans blocked a Democratic-led attempt to curb Trump’s war-making powers on Thursday, Pennsylvania congresswoman Madeleine Dean said pursuing impeachment or calling for the president’s removal by the 25th amendment was not the “best use” of Democrats’ time. Dean, who played a central role in Trump’s second impeachment trial, said Democrats’ priority should be trying to claw back Congress’s war-making authority and win back the majority in this November’s midterm elections.

“He is eligible for and should be held to impeachment,” she said. “But that’s not the fight right now. Right now, we have to end this war.”

Democratic leaders have said they will continue to force war powers resolutions on the Iran war, as the effort appears to be gaining traction. The Trump administration is also facing demands for more Congressional briefings on the war – and to justify its request for hundreds of billions of dollars in new defense spending.

“Congress must reassert its authority, especially at this dangerous moment,” the Senate minority leader Chuck Schumer said at a press conference this week. “No president, Democrat or Republican, should take this country to war alone. Not now. Not ever.”

Public opinion polls show Americans broadly disapprove of the conflict. A survey by the Pew Research Center, found that nearly two-thirds of Americans lacked confidence in Trump’s ability to make good decisions when it comes to Iran, as they expressed deep concern about rising gas prices. Meanwhile, consumer sentiment sank across age, income, and political party to a record low, a new University of Michigan survey found.

For Democrats, the war has further fueled questions about the party’s relationship with Israel, as its standing among Americans plummets, especially among young people. Progressive candidates have channeled the issue into their messaging and their fundraising appeals, accusing their opponents of taking donations from groups affiliated with American Israel Public Affairs Committee (Aipac), the prominent pro-Israel lobby group.

Tensions have flared in Michigan, where Abdul El-Sayed is running for Democratic Senate nomination in a swing state with a large Arab American population still furious over the party’s support for Israel’s war in Gaza.

El-Sayed is one of several progressives who are challenging more establishment-backed rivals over the Iran conflict, pressing the party to stop accepting donations from weapons manufacturers and Aipac. His decision to campaign with leftwing streamer Hasan Piker last week drew sharp criticism from his Democratic opponents and Jewish leaders, who assailed Piker as antisemitic – a charge Piker denies – and demanding the left refuse to platform him.

“Every dollar that we spend on an aimless, illegal, unjustified war in Iran that allows Israel to annex southern Lebanon and destroy people and their lives, is a dollar not spent to improve our schools, provide people with healthcare and fix our broken infrastructure,” El-Sayed told the Guardian recently.

During a meeting in New Orleans this week, members of the Democratic National Committee rejected a symbolic resolution that singled out Aipac in Democratic primaries and deferred two further resolutions on Middle East policy to a working group that critics say has been woefully slow to act. Ken Martin, the DNC chair, endorsed the approach.

Allison Minnerly, the Florida Democrat who sponsored the Aipac resolution, said the party’s leadership “really does not want to continue having this conversation” but insisted “our voters, our base, does”.

“These are hard questions on a local and national level, but the DNC ultimately has to not just kick things down the road but address things head on because people are tired of waiting,” she said.

This week, the progressive activist group MoveOn launched a “Stop the War Hawks” campaign, which it says will target candidates with financial ties to defense contractors and pro-Israel PACs. In New York’s 10th congressional district, the organization endorsed Brad Lander against congressman Daniel Goldman, citing Goldman’s support for unconditional military aid and ties to Aipac.

In a statement, Joel Payne, the group’s chief communications officer, argued that the campaign was a reflection of the anti-war left’s growing influence.

“The grassroots mandate is clear,” he said. “It’s time to retire Democrats who would rather do the bidding of big money, Maga-aligned war hawks than restore healthcare and lower costs for American families.”

Nearly every Congressional Democrat is opposed to Trump’s bombing campaign, noted Jim Kessler, executive vice president for policy at the centrist thinktank Third Way. He said efforts by progressives to draw sharp lines between Democratic candidates by elevating issues like Aipac funding or donor purity risks undermining the party’s chances in this year’s midterm elections – and in 2028.

“If we have a Democratic nomination in which the top-issue litmus tests are miles away from what the average voter cares about,” Kessler cautioned, “we will throw this election away.”

As the shadow primary for 2028 ramps up, Democratic hopefuls will have to contend with a world dramatically changed by Trump’s second presidency, said Thomas Wright, a senior fellow at the Brookings Institution and former National Security Council official.

With more than two years left in his presidency, Trump has already demonstrated his willingness to forcefully exert military power abroad, wage a global trade war, sideline longstanding allies and forge new relationships with strongmen, leaving many Americans disoriented and disillusioned, especially the president’s supporters who had believed his promise of new wars.

“There’s a sense that things won’t come back to the way they were,” Wright said. “The message President Biden came in with – ‘America’s back, things are back to normal’ – I don’t think that’s what Americans feel or think now, let alone the rest of the world.”

This week, more than a half-dozen potential Democratic 2028 candidates appeared at the National Action Network conference in New York, where they were asked to weigh in on a conflict that appears far from over. They offered sharp condemnation of Trump’s approach, questioning the war’s costs and risks.

“The United States military is the best military in the history of the world,” Maryland governor and combat veteran Wes Moore said on Thursday. “There is nothing that the United States military, militarily, cannot do, [but] the question is: should we be doing it? And I do not think that the president of the United States has answered that question.”

Shah, of Common Defense, said it was easy for Democrats to oppose military action with Trump in the White House. But in the weeks and months ahead, he hopes Democrats will engage in a far more robust debate around its foreign policy vision – one that prioritizes diplomacy and deterrence and reserves military force as a last resort.

“If Democrats try to paper over these issues, like they did with Gaza in 24,” he said, “they risk not only losing the midterms, but repeating the mistakes that led us to spend 20 years in Iraq and Afghanistan.”