Human Rights Watch warns that “Yemen is the world’s largest humanitarian crisis. It stands on the brink of a famine years in the making: Half of its population, 14 million people, may starve if something does not change.” The United States can foster change by ending all US support for the Saudi-led assault on the poorest country in the Arab world.

Speaker Paul Ryan and his allies in the House Republican Caucus have blocked a move by Congressman Ro Khanna to get the United States on the right side of history. But there is still a chance the Senate might do the right thing. And Bernie Sanders is determined to do everything in his power to make that happen.

Earlier this year, the senator from Vermont tried unsuccessfully to force a Senate vote on his proposal to block continued US aid for the military missions of the Saudis in Yemen unless US involvement is authorized by Congress. The March attempt won 44 votes (including those of five Republicans).

In the final weeks in the 115th Congress, Sanders has renewed his drive to put the crisis in Yemen on the agenda, and the senator and his allies could get a vote on ending US aid to the Saudis this week. As The Washington Post reports, “The expected vote on a measure to invoke the War Powers Resolution—likely to take place Wednesday or Thursday—will be the first test of whether the slaying of Saudi Arabian journalist Jamal Khashoggi has broken Congress’s long-standing pattern of prioritizing the sanctity of the US-Saudi alliance through weapons sales and other cooperative military ventures over repeated, documented human rights violations.”

The legislative maneuvering on behalf of Senate action been inspired by the combination of principle and practicality that so frequently motivates Sanders when it comes to global affairs. Though the senator is invariably portrayed in media accounts as a domestically focused economic populist, he has a long history of engagement with international human-rights issues and humanitarian concerns.

Sanders, who has been arguing in recent months for a new focus on progressive internationalism and who this weekend will draw attention to the project in forums with domestic and international figures in Vermont, sees an opening in the lame-duck session of the Senate to press for a clear signal regarding the fighting in Yemen. “We should not be allied with a dictatorship like Saudi Arabia who is leading the effort in that war,” explains Sanders. “Further, in my view, that war is unconstitutional because Congress, which has the war-making authority in our form of government, has not authorized it. Let’s get out of Yemen as soon as possible and help bring humanitarian help to that struggling country.”

To that end, the senator has been angling since October to “bring Senate Joint Resolution 54 back to the floor for another vote, so the Senate can compel an end to US participation in the Yemen war as a matter of law, not simply as a matter of the president’s discretion.”

Sanders recognizes an opening “for the United States to redefine our relationship with the Kingdom of Saudi Arabia.”

With increased global attention to the metastasizing crisis in Yemen—where the United Nations Office for the Coordination of Humanitarian Affairs now says that “an alarming 22.2 million people in Yemen need some kind of humanitarian or protection assistance”—there have been signs that US officials are growing uncomfortable with the excesses of the Saudis. Even as Washington has reportedly “slammed the brakes” on a United Nations Security Council resolution that seeks a limited cease-fire in Yemen, the Pentagon has said it plans to halt US refueling of Saudi aircraft involved in bombing raids that have destroyed hospitals, food supplies, and civilian infrastructure while killing and injuring thousands.

But that is, at best, a half step. President Trump continues to send signals that position the United States on the side of the Saudis in the Yemen conflict—at the same time as he continues to make excuses for Crown Prince Mohammed bin Salman amid the international outcry over the killing of Khashoggi. As William Hartung, the director of the Arms and Security Project at the Center for International Policy, has explained: “[If] President Donald Trump and his foreign policy team really want to end the war, they need to use all the tools at their disposal—military, diplomatic and economic.”

“Trump seems unlikely to do so,” argues Hartung. “In fact, it’s more likely that the US will remain complicit in the civilian deaths that have resulted from Saudi attacks. It is therefore imperative that Congress hold Trump’s feet to the fire by passing legislation that invokes the War Powers Resolution, which bars the United States from playing a substantial role in any conflict that has not been authorized by Congress.”

Sanders agrees. He notes that after the Senate tabled his war-powers resolution in March, “This crisis has only gotten worse since then, and our complicity even greater.” To address that complicity, Sanders says the Senate must act to “show the Saudi government that they do not have a blank check from the United States to continue human rights violations.”

The measure the senator has proposed, “S.J.Res.54—A joint resolution to direct the removal of United States Armed Forces from hostilities in the Republic of Yemen that have not been authorized by Congress,“ now has 16 co-sponsors. A pair of key Democrats—California Senator Kamala Harris, like Sanders a 2020 presidential prospect, and Virginia Senator Tim Kaine, the party’s 2016 vice-presidential nominee—added their names to the list this month. Utah Senator Mike Lee, a Republican who has a history of breaking with the president and party leaders on war-and-peace issues, remains a stalwart supporter. Perhaps most significantly, New Jersey Senator Robert Menendez, the ranking Democrat on the Foreign Relations Committee, who cast a “no” vote in March, has indicated that he now backs the Sanders proposal.

Activists groups such as Peace Action and MoveOn have launched a #YemenCantWait lobbying push. Code Pink co-founder Medea Benjamin is amplifying the “Vote yes on S.J.RES.54” campaign with a core message that “From the ongoing war in #Yemen to the gruesome murder of #JamalKhashoggi, U.S. support for Saudi Arabia must end.” At an urgent moment, when so many lives are at stake, Sanders is making the case that the Senate can and must address the humanitarian crisis in Yemen and the constitutional crisis in a US Capitol where, for too long, Congress has failed to check and balance the war powers of presidents.

“I’m glad that the Trump administration is ending US refueling of Saudi aircraft in Yemen’s devastating war,” acknowledges Sanders. But that is insufficient. The Senate, he says, must declare, in no uncertain terms, that “US participation in this conflict is unauthorized and unconstitutional and must end completely.”