Secretary of State Mike Pompeo’s briefing to legislators last week went so badly that it may have galvanized Republican support to restrain President Trump from war with Iran, Sen. Tim Kaine (D-VA) told The Daily Beast on Tuesday.

Kaine, who will soon introduce a resolution to require Congress’ approval before any such escalation of hostilities, now believes there are as many as a dozen potential GOP votes in the Senate—far more than expected, and also far more Republicans than were willing to vote on a similar initiative to get the U.S. out of the Saudi-led war in Yemen in 2018.

“I wish I could say that the getting sponsors has been because I'm so persuasive,” Kaine told The Daily Beast. At last Wednesday’s briefing to senators, the senator said there was “an air of dismissiveness about the role of Congress” from Pompeo and the other briefers.

“There were a couple of other problems I thought about that briefing,” Kaine added. “Without getting into classified information, many of us were underwhelmed by the evidence of imminence. Not everybody was, some thought it was fine, but many of us were underwhelmed by that.”

Several legislators left that briefing last week infuriated with what they considered evasive or dismissive answers on a question of war and peace. Memorably, Utah Republican Sen. Mike Lee, a close ally of the president, laced into the briefers—Pompeo, CIA Director Gina Haspel, Defense Secretary Mark Esper, and Acting Director of National Intelligence Joseph Maguire—for “telling us that we need to be good little boys and girls and run along and not debate this in public.” Several others predicted to The Daily Beast that it would cost the administration congressional support over Iran ahead of the upcoming war-powers votes.

Since last week, Kaine has been in talks with GOP senators—including Lee, Sens. Rand Paul (R-KY), Susan Collins (R-ME) and Todd Young (R-IN)—about shaping the text of his resolution in hopes of it garnering as much Republican support as possible.Those negotiations, Kaine said, have yielded compromise—including mutual support of striking text from the resolution that specifically mentions President Donald Trump. “We’re trying to make it as palatable as we can for everybody,” he said.

Such efforts have proven fruitful so far. Young told reporters on Tuesday that he’d be backing Kaine’s resolution—and with Lee and Paul already supportive, only one more GOP senator is needed to support the measure in order for it to pass the Senate.

Kaine said he wasn’t sure how large the pool of possible GOP ‘yes’ votes is. “Probably a dozen, but I could be surprised,” he said. Lee, meanwhile, predicted to reporters that it would probably be close to the bloc of seven who voted with Democrats on the Yemen resolution.

Last week, the House of Representatives passed a similar Iran war powers resolution by a 224 to 194 margin. That resolution, led by Michigan Democrat Elissa Slotkin, is unlikely to receive a Senate vote, however. It is what’s known as a “concurrent” resolution—which, owing to obscure parliamentary procedure, doesn’t provide an obvious mechanism for senators to get it onto the floor for a vote.

Slotkin’s measure, as a concurrent resolution, also doesn’t require a presidential signature to pass. House Democratic leadership considered that a strength, since it avoids a presidential veto—something Trump exercised when Congress voted to get the U.S. out of the Yemen war. But avoiding a veto has an upside for Trump, argued Matt Duss, the chief foreign policy adviser to Sen. Bernie Sanders (D-VT).

“If Trump wants to veto the second War Powers Resolution of his presidency and assert a unilateral right to escalate conflicts as he’s sending thousands more troops to the Middle East, he can do that, but it will just further reveal that he’s lying when he says he wants to end our country’s endless wars,” Duss told The Daily Beast.

A representative for Slotkin did not immediately respond to requests for comment.

In response, some Senate Democrats advocate passing the Kaine resolution and sending that back to the House, where the Democratic-controlled chamber can procure passage of a counterpart to send to the White House. Kaine said he was optimistic his bill would pass the House. In order to override a likely Trump veto, however, two-thirds support will be required from both chambers of Congress—a bar that the Senate will likely fail to meet.

“I think it's a good thing to get this bill on the president's desk, you know, veto or not. We do our job, he does his,” Kaine said. “This is about Congress—it's about Congress, because Congress has been the one that's kind of been willing to be a backbencher on this. It's time for us to stop.

Hours after this story went to press, Joe Gould of Defense News tweeted that Kaine says he has four Republican votes—from Lee, Rand Paul, Todd Young and Susan Collins—that put support for his resolution at 51 senators.