A heavyweight right-wing financier has thrown in with a left-right coalition to end the U.S. military’s involvement in the Saudi-led war on Yemen, one of the world’s most devastating humanitarian catastrophes, The Daily Beast has learned.

The Charles Koch Institute, bearing the brand of one of the most influential sources of conservative political money, is backing an effort spearheaded by progressive California Democrat Ro Khanna to demand either an end to non-counterterrorism aid to the Yemen war or a direct congressional vote authorizing it.

Multiple congressional and allied sources told The Daily Beast they plan to bring their resolution to a vote in the House during the November lame-duck session after the midterm elections. And they think they can win.

This cross-ideological coalition has tried and failed before—most recently, in March, when Sens. Bernie Sanders of Vermont, Chris Murphy of Connecticut and Mike Lee of Utah lost 55-44 to end American midair refueling and intelligence support for the Saudi and Emirati forces assaulting Yemen. But this time, the antiwar legislators and their allies believe bipartisan outrage at Saudi Crown Prince Mohammed bin Salman—an architect of the three-year old war—over his apparent decision to order the murder of journalist Jamal Khashoggi can put them over the top.

“Given divergent strategic interests and very different values, the United States has long needed to modify our relationship with Saudi Arabia. Riyadh’s callous prosecution of a war in Yemen that undermines our interests and the heinous murder of Khashoggi both underscore this,” said the Charles Koch Institute’s vice president of research and policy, William Ruger. “A realistic foreign policy often requires difficult trade-offs when security needs and values collide. But in this case, they are in harmony such that we can safely change our approach.”

The Khanna-led resolution, H. Con. Res. 138, invokes the 1973 War Powers Resolution to hold the U.S. end of the Yemen war insufficiently authorized. If passed, it would start a 30-day countdown for the U.S. military to cease refueling Saudi warplanes and providing intelligence on potential targets. Any additional U.S. involvement to a war that has brought a staggering 14 million people to the brink of starvation would require the Trump administration to formally request congressional authorization. If the end of U.S. involvement wouldn’t necessarily ground Saudi warplanes, it would certainly deal Riyadh’s brutal air war a substantial setback.

The resolution would not, however, compel any change in U.S. attacks on al-Qaeda targets in Yemen, against which there have been an 32 air strikes in 2018 so far, an intensification from the final year of the Obama administration.

But the administration, which has aligned firmly with both the Saudis and the Emiratis, claims the resolution’s premise is fatally flawed. “The limited military and intelligence support that the United States is providing to the [Saudi]-led coalition does not involve any introduction of U.S. forces into hostilities for purposes of the War Powers Resolution,” the Pentagon’s acting top attorney, William S. Castle, wrote to Mitch McConnell ahead of the vote on the Sanders-Murphy-Lee resolution.

The resolution’s backers consider that sophistry. Just because the U.S. isn’t deploying ground troops to Yemen doesn’t make U.S. participation in the war any less real, they say, or any more congressionally authorized. And they also see congressional antipathy rising after Secretary of State Mike Pompeo and Defense Secretary Jim Mattis credulously insisted last month that the Saudis are taking care to avoid civilian casualties.

That’s where the Kochs and their allies come in.

The Koch Institute’s tax status means it can’t lobby for the resolution. Instead, it’s briefing conservative lawmakers to enlist their support when Khanna’s resolution reaches the floor next month. Its allies at FreedomWorks, also influential on the right, are free to lobby, and have been pressing the Yemen issue in recent discussions with congressional Republicans since last year, when it threw its support behind the Sanders-Murphy-Lee effort.

In addition to the arguments they’re making about Yemen itself, the rightward edge of the coalition is pressing Republicans on stopping the American end to a war that has never been authorized, let alone declared, by Congress, and framing it as a matter of core conservative principles. “Anybody who cares about the constitution should vote for this,” said Sarah Anderson, who handles foreign policy for FreedomWorks.

The resolution already has the support of Republicans like North Carolina’s Walter Jones, Kentucky’s Thomas Massie and Ken Buck of Colorado, whose rules-committee perch the resolution’s backers consider a bulwark against legislative shenanigans. (A previous House effort condemning the Yemen war passed overwhelmingly last year, but without any teeth to end U.S. support.) A Koch Institute staffer also said the Trump-aligned Freedom Caucus was a potential source of votes, and members considered persuadable include Ted Yoho of Florida and Raul Labrador of Idaho.

All of which has convinced the resolution’s backers that they stand a real chance at victory. A House Democratic aide believes that if they can pass the resolution in the House, the Senate will quickly follow—and since it’s a concurrent resolution, it won’t go to President Trump for a potential veto.

Next months’ vote on the resolution “is going to be the referendum on the U.S.-Saudi military alliance,” the Democratic aide continued. “Fourteen million people are going to die of starvation in months if we don’t act.”