Collins questioned how a requirement that one House committee with oversight of Medicaid could find more than half of the overall desired savings without touching that program.

“I don’t know how the instruction to the Energy and Commerce Committee of $880 billion can be met without cutting benefits from Medicaid, but I may be wrong,” she said. “Maybe they have some magic formula.”

Added another key swing vote, Sen. Lisa Murkowski of Alaska: “I’m concerned about how we’re going to figure out how we do this between the two bodies. I’m gonna be worried about Medicaid until we get on the other side of this so I don’t have to be worried about Medicaid.”

Thune signaled he understands he’ll have to bridge the divide.

“We got folks on both sides of that issue,” the South Dakota Republican said when asked about concerns that the $1.5 trillion in spending cuts is too high. “We’ll have to sort it out.”

Leadership tensions flare behind the scenes

In a single week, GOP leaders flipped dozens of holdouts — some 64, by one leadership aide’s count — to take the procedural leap to unlock the reconciliation process. And Republicans insist they can do it again on the final bill, saying Johnson has proved his skeptics wrong time and again — whether it’s been about a March spending bill to keep the government open, winning the speaker’s gavel in January or this latest battle that led to a cliffhanger vote on the House floor.

“Nothing ever comes easy in the US House,” said Republican Rep. Dusty Johnson, a leadership ally, who acknowledged the GOP conference is full of people with “strong opinions on most everything.”

“There’ve been a lot of people who have counted us out every single time,” said Johnson, a South Dakota congressman. “We have won despite that, and we’re gonna win this time too.”

But some fissures have begun to show among the speaker’s leadership team. On Wednesday night, for instance, House Majority Whip Tom Emmer and his whip team believed they had narrowed the “no” votes down to a point where they could vote instead of punting until the next morning, according to three people familiar with the discussions.

Then, Mike Johnson — under pressure from conservatives demanding a meeting — decided to call a joint meeting of the roughly 20 holdouts during the vote, where GOP leaders seemed to lose ground. That left Emmer furious, those people familiar said.

But separately, people close to Johnson and House Majority Leader Steve Scalise said it was their work cajoling the holdouts that got Republicans across the finish line. They said Emmer was not in late Wednesday night meetings.

Part of the frustration comes from the motley gang of GOP holdouts, who were at times unclear about exactly what they wanted. For the next steps of Trump’s megabill, though, those hardliners are clear: $1.5 trillion in cuts or bust.

“We made it pretty clear that if we don’t pay for what we spend — no more deficit spending — we can go right back. And we will. And they know that,” Rep. Ralph Norman of South Carolina said.

Rep. Chip Roy, another hardliner who has vowed to hold the line on that minimum threshold of cuts, said of his GOP counterparts: “They better get committed.”

“If it ends up being all tax cuts and no [spending] cuts, it’s not going to pass the House,” the Texas Republican added.

Those fiscal hawks insisted they didn’t cave on the final blueprint. But Rep. Thomas Massie of Kentucky told CNN they should be wary of what they were promised.

“I knew all along they would trade the cow for magic beans,” said Massie, one of just two Republicans who voted against the budget blueprint. “These beans are like the rest. They don’t sprout.”

CNN’s Alison Main and Ted Barrett contributed to this report.