While most Senate Republicans favor broad executive authority on military intervention, a handful have broken ranks with the caucus and joined Democrats when it comes to the United States’ military posture on Iran or in Yemen.

Last summer, four Republicans broke with their party to support an amendment offered by Kaine and Sen. Tom Udall (D-N.M.) to require congressional approval for military action against Iran: Sens. Susan Collins of Maine, Jerry Moran of Kansas, Rand Paul of Kentucky and Mike Lee of Utah.

In the months since the unsuccessful Senate vote, tensions in the Middle East have reached a boiling point.

Paul said on Monday he supports the concept of Kaine’s resolution and plans to discuss the details with the Virginia Democrat.

“The death of Soleimani, I think, is the death of diplomacy,” Paul said. “There are people who do believe that Congress should declare war, and there’s more than just me on that. … There have also been some people on both sides who have been consistent in saying that we can’t give up this power.”

Sen. Rand Paul. | J. Scott Applewhite/AP Photo

Collins said she wants “to look at the specifics” of Kaine’s proposal, but added that “it is important he not infringe on the president’s role as commander in chief to respond to an imminent threat.”

“This is one where the language really matters,” she said.

The Democratic-led House, meanwhile, is slated to pass its own War Powers resolution this week that is similar to Kaine’s proposal.

Democrats see the measure as a way to force senators to go on the record with whether they support a war with Iran. Democratic lawmakers were quick to call for further military action to be authorized by Congress, warning that the situation could spiral out of control. Iranian leaders have threatened retaliation after Soleimani’s death, and the Iraqi Parliament on Sunday approved a nonbinding resolution calling for the removal of U.S. troops.

The Senate and House resolutions come after top Democrats were not given advance notice from the Trump administration about the strike that killed Soleimani in Iraq. The White House sent a classified War Powers notification to Congress after the attack, which Senate Minority Leader Chuck Schumer and ranking member of the Senate Foreign Relations Committee, Sen. Robert Menendez (D-N.J.), have requested that the administration declassify.

Secretary of State Mike Pompeo, Secretary of Defense Mark Esper, Joint Chiefs of Staff Chairman Mark Milley and CIA Director Gina Haspel are slated to brief senators on Iran on Wednesday afternoon, according to a Senate staffer.

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Most Republicans have praised the administration for Soleimani’s killing, and many argue that the U.S. was responding to an imminent threat from Iran. Trump, they say, acted within his authority.

“The Constitution authorizes the president to defend the United States and our service members and our interests without coming to Congress,” Sen. John Cornyn (R-Texas) said.

But Senate Democrats remain optimistic they can peel off Republicans who either supported the Iran amendment or voted to end U.S. support for the Saudi-backed war in Yemen. Among the Senate Republicans who backed the Yemen resolution are Lee and Todd Young of Indiana. Lee has not indicated whether he would support Kaine’s resolution but described Soleimani’s death as “a big victory for the safety of the American people.”

Young said Monday he has “a lot of respect for Sen. Kaine” and that he’ll “take a look at whatever he’s drafted.”

Kaine said he has yet to survey his colleagues but that the Senate’s recent votes on Iran and Yemen are cause for optimism.

“Nobody was interested in it when I came here in 2013, except me,” Kaine said. “We’re getting my votes on these things now. More people are interested. … We should be the ones declaring war, not the president."

Burgess Everett and John Bresnahan contributed to this report.