Progressive activists say they’re dismayed that senior congressional Democrats aren’t more strongly condemning President Donald Trump’s strikes against Syria on Thursday night.

Some Democrats in Congress dinged Trump on the process — not seeking congressional approval — but largely supported the action itself. Senate Minority Leader Chuck Schumer (D-NY) called punishing Syria’s Bashar al-Assad “the right thing to do,” and House Minority Leader Nancy Pelosi (D-CA) labeled the strikes a “proportional response.” Pelosi has also called for the House to end its recess and reconvene to discuss the attacks.

But left-wing organizers want Schumer and Pelosi pushing back more strongly. “Democrats are acting like a bunch of cowards,” said Murshed Zaheed, political director at CREDO Action, a left-wing grassroots advocacy organization. “We are calling on all congressional leaders to call for emergency deliberations on Trump’s illegal escalation in Syria. Anything short of that will show that Democrats are completely out of touch with the base of their party.”

Rep. Ro Khanna (D-CA), a progressive first-term member who represents Silicon Valley, broke with Democratic leadership. “Let's be blunt: The problem with process arguments is it's not the substantive question,” he said. “The question is: Where do you stand on issues of war and peace? Do you believe it's more unilateral military intervention? Did we learn the lessons of Iraq and Libya and that we should not be engaged? I wish the Democratic Party would speak to the substance of that issue.”

The progressive left has been skeptical of military intervention, vocally opposing Hillary Clinton’s hawkish views, and now say they’re preparing for a new fight over Syria with the left’s closest allies on Capitol Hill.

Trump launched a military strike against a Syrian government airbase Thursday night in response to a gas attack by the regime last week. With the exception of Sen. Rand Paul (R-KY), Republicans in Congress overwhelmingly praised the decision.

“[Democrats] haven’t done nearly enough — they need to explicitly call out that this was a reckless military action that does not make us more safe, and that you can’t launch strikes without a clear plan. We have not heard that from Democratic leadership,” said Neil Sroka, communications director for the left-wing organizing platform Democracy for America.

Added Ben Wikler, Washington director of MoveOn.org: “We appreciate the call to stay in session, but we haven’t heard from Democratic leadership a sharp response or criticism of the unilateral use of warmaking power from the president of the United States. We need their voices now.”

Progressive groups are mobilizing against Democrats over Syria

Some Democrats further to the left on the political spectrum have reacted more critically to the attacks than the party’s senior congressional leadership. In a statement, Rep. Keith Ellison (D-MN) and the House Progressive Caucus said the assault “could pull the United States into a regional war and escalate this unprecedented humanitarian crisis.”

Meanwhile, Sens. Chris Murphy (D-CT) and Bernie Sanders (I-VT) put out statements cautioning against further escalation and criticizing Trump for not seeking prior congressional authorization. Sen. Kirsten Gillibrand (D-NY), a possible 2020 presidential contender, called the strikes cause for “grave concern.” The vast majority of Senate Democrats have rallied behind the demand that Trump should brief Congress and seek a renewal of the Authorization for Use of Military Force before expanding military action.

But at least four House Democrats — Reps. Tulsi Gabbard (D-HI), Barbara Lee (D-CA), Khanna, and Ted Lieu (D-CA) — have fiercely denounced Trump’s attacks as being of questionable legality and dubious planning.

Added Rep. Pramila Jayapal (D-WA) in an interview: “Saying that it’s a proportional response ignores the fact that any kind of a response that involves military use should have come to congress for us to talk through. You’re ignoring the ramifications of what happens after this response.”

“Some Democrats have come out of the gate swinging, and that’s great,” said Wikler. Still, he argued that both the party’s most powerful members and the bulk of its caucus were not sufficiently stressing the dangers of the action Trump has already taken.

In a floor speech on Friday, Schumer demanded that Trump “come up with a coherent strategy and consult with Congress before implementing it.”

Wikler said that’s not good enough. “As a party, they’re not channeling the concern that Trump could be a Tomahawk missile in a China shop,” Wikler said.

Given that Trump is the commander in chief and that many Democrats did not protest Barack Obama’s foreign interventions without congressional approval, this may be a hard case for Democrats to make. But Wikler said this is exactly what its progressive base wants — for Democrats to harp on what they see as Trump’s impulsive and brash decision to attack Syria after growing personally upset over photographs he saw of the atrocities.

“The primary concern right now is that too many Democrats in Congress are not strongly enough insisting Congress hold Donald Trump accountable and make sure he doesn’t start World War III accidentally,” Sroka said. “If you’re not aggressively calling out the lack of strategic planning here, you’re giving credence to a president who can’t even call an ally without screwing it up.”

“There’s a chance here for new leadership to form”

On Friday afternoon, MoveOn will hold an emergency meeting to solicit feedback from its members and discuss how to respond to congressional Democrats who have embraced Trump’s strikes.

Some groups are moving faster. Justice Democrats, a new progressive organization founded in the wake of Trump’s election, says it will look to run primary challenges against congressional Democrats who do not speak out strongly against Trump’s Syrian attacks.

“We’re going to be looking for incumbents to challenge those who don’t take proper stances here,” said Corbyn Trent, a spokesperson for the group.

Of course, the duration of the campaign will help determine if it becomes a dividing line within the Democratic Party. But it wouldn’t be the first time a Democrat rose to prominence on the basis of breaking with his party on matters of war and peace. Obama, of course, most famously emerged after declaring his opposition to the Iraq War in Chicago in 2002.

Trent says the opportunity may be emerging for Democrats willing to speak to the country’s antiwar base, which he said was far wider than Senate Democrats realize.

“There’s a chance here for new leadership to form, for it to shift,” Trent said. “There may be a new breed of leaders willing to take stands on Syria, and that could shift the power of the party in the upcoming elections.”