A small band of Republican senators on Thursday broke with President Trump to advance a resolution which would limit his ability to launch additional strikes on Venezuela. Despite being briefed by top administration officials this week, lawmakers on Capitol Hill are not being shy about their concerns over what comes next for the oil-rich South American nation. 

Senator Tim Kaine has called up several War Powers Resolutions in recent months, though this is the first one to pass the chamber. The Republicans who joined him — Senators Rand Paul, Lisa Murkowski, Susan Collins, Todd Young, and Josh Hawley — have said they do not have enough clarity around what the administration will do next. 

“The President and members of his team have stated that the United States now ‘runs’ Venezuela. It is unclear if that means that an American military presence will be required to stabilize the country,” Mr. Young said in a statement after the vote. “The Constitution requires that Congress first authorize operations involving American boots on the ground.”

Though this was Mr. Young’s first time backing one of Mr. Kaine’s resolutions, several other Republicans have been voting with Democrats for months. Ms. Murkowski voted for a similar measure last year before the operation to capture President Maduro took place on Saturday. 

“​​I took these votes because I believed the administration failed to provide Congress with the information necessary to fully evaluate the legal basis for these escalating actions,” she said after the raid on Mr. Maduro’s compound, explaining her past support of limiting Mr. Trump’s powers. “That was true then, and it remains true today.”

Dr. Paul has also been supporting Mr. Kaine’s past resolutions, saying that it is Congress which must be supreme in declaring war or granting the president the authority to launch new military campaigns. 

“Who among the Framers would have ever guessed or conceived of a time when Congress would lack any ambition — any ambition at all? Who would have predicted a time when Congress would be so feckless as to simply and obediently abandon all pretense of responsibility and any semblance of duty so as to cede the war power so completely to the president?” Dr. Paul asked rhetorically on the Senate floor Wednesday. 

“The majority party has lost its grip and become eunuchs in the thrall of presidential domination,” he said of his own Republican colleagues. 

Mr. Kaine’s War Powers Resolution will now be debated on the floor of the Senate, where its fate is still unknown. Democrats need at least four GOP lawmakers to vote with them in order to advance the measure, assuming all members of the minority vote for the resolution. 

One Democrat has already hinted that he may vote against Mr. Kaine’s resolution — Senator John Fetterman. Though he voted yes on the motion to proceed on Thursday, he left the door open to voting against final passage next week. 

“I voted AYE on this resolution to discharge it from the Senate Foreign Relations Committee so we can continue this important debate on the floor of the Senate,” he said simply on Thursday. 

Mr. Trump responded to the advancement of the resolution on Thursday, saying that Republicans should be “ashamed” of those five colleagues who voted with Democrats. The president says that those five lawmakers should not be re-elected, including Ms. Collins, who is set to face one of the most competitive Senate campaigns this fall, given she is the only Republican running in a state that Vice President Kamala Harris won in the last presidential race. 

If the resolution does pass the Senate, then the House will likely take it up before the end of January. There is a possibility that it could pass, given Speaker Mike Johnson’s narrow margins. 

Congressman Thomas Massie has already made clear that he would vote for the resolution once it comes up. Congressman Don Bacon — a former Air Force brigadier general who is retiring this year — has also left the door open to supporting the resolution. If those two Republicans break with their party to vote with Democrats, then Mr. Johnson will be able to lose only one additional GOP lawmaker on the vote. 

Despite briefings from top administration officials this week, some lawmakers in Congress still harbor deep reservations about Mr. Trump’s insistence that America is now going to control Venezuela’s oil supply. The top Democrat on the House Foreign Affairs Committee, Congressman Greg Meeks, told the New York Sun on Wednesday that he asked the briefers about the future of Venezuela, but walked away with no substantive answers. 

“No plan has been proposed — no plan. No talking of democracy at all. The president has an issue with the word democracy or concern about the people of Venezuela,” Mr. Meeks said. “All he says is, ‘We’re going to take their oil. We’re going to sell their oil.’”

“I walk away nervous and very concerned about the people of Venezuela,” he added.