The latest Republican effort to unwind the Affordable Care Act collapsed Monday as a third GOP senator announced her opposition and left the proposal short of the votes needed to pass.

While one top Republican senator held out the possibility that the Senate might still vote on the bill, others accepted the reality that the push had sputtered out after Sen. Susan Collins (R-Maine) joined two of her colleagues in formal opposition.

"Everybody knows that's going to fail," said Senate Finance Committee Chairman Orrin G. Hatch (R-Utah), who led a raucous, five-hour hearing on the bill Monday afternoon. "You don't have one Democrat vote for it. So it's going to fail."

Monday's developments amounted to a massive setback for Senate Majority Leader Mitch McConnell (R-Ky.) and President Trump, who spent the past week trying to rally support for a last-ditch attempt to fulfill a seven-year Republican promise. The effort lost much of its steam in the past four days, as it became clear that the new proposal had not resolved the same disagreements that plagued Republicans in a failed July push.

Collins announced that she could not back the measure — which would redistribute federal health-care funding across the country and sharply curb spending on Medicaid — moments after the release of a much-anticipated Congressional Budget Office analysis that forecast "millions" of Americans would lose coverage by 2026 if the bill was enacted.

Two GOP senators — Rand Paul (Ky.) and John McCain (Ariz.) — had already come out against the bill and were not swayed by a new draft that emerged Monday morning. Republicans hold a 52-to-48 advantage in the Senate; they can lose only two votes from their party and still pass legislation with the help of a tiebreaking vote from Vice President Pence.

A fourth Republican, Sen. Ted Cruz (Tex.), indicated through his aides Monday that he could not back the bill in its current form because it would not go far enough in repealing the 2010 law.

Senate Majority Whip John Cornyn (R-Tex.) did not rule out the possibility of holding a vote on the proposal despite clear signs that it did not have sufficient support to pass. Many Republicans feel pressure from voters to keep pushing to repeal the ACA before moving on to other issues.

"There are a lot of people who want to vote yes and be recorded as voting yes," Cornyn said, adding that the Republican conference would decide the matter Tuesday, when lawmakers will meet for the first time since leaving for recess last week. "I think there is some advantage to showing you're trying and doing the best you can."

Neither a series of last-minute changes over the weekend nor the CBO's preliminary analysis managed to shift any votes in the bill's favor. If anything, the CBO report worsened the proposal's chances by noting that it was impossible to forecast the number of Americans likely to lose coverage but that "the direction of the effect is clear." The report also estimated a $1 trillion loss of federal funding for Medicaid by 2026.

Collins delivered a scathing assessment of the bill in a statement, saying the fourth version that the senators had produced in an effort to win new votes "is as deeply flawed as the previous iterations."

Speaking to reporters Monday evening, the senator said the administration had lobbied her hard to endorse the bill — and she received a call from the president himself before the CBO score was announced.

"I told him that I would go back and look at the numbers one more time, but I was straightforward with him that I was not likely to be a yes vote," she said, adding that the process had been too hasty. "Last night, a whole new bill came out, which to me epitomizes the problem."

Speaking on the Senate floor Monday, McConnell thanked Sens. Bill Cassidy (R-La.) and Lindsey O. Graham (R-S.C.), the bill's authors, but suggested that their work had stalled out. He thanked other lawmakers and committees of jurisdiction, as one might do at the official conclusion of a legislative push.

"I'd like to thank each of these committees, their chairs, their members and their staffs for their hard work to provide the American people with a better way than Obamacare and its years of failures," McConnell said.

The legislation's sponsors had rewritten the bill to deliver more money to Alaska and Maine, in the hopes of winning over Collins and Sen. Lisa Murkowski (Alaska), another key GOP centrist.

[Latest GOP effort to dismantle Obamacare on the brink of failure after defections]

The contentious debate erupted into public view Monday afternoon as protesters chanted so loudly at the hearing's outset that Hatch was forced to temporarily adjourn as police officers arrested and removed 181 of them.

"No cuts to Medicaid! Save our liberty!" one woman in a wheelchair screamed as she was wheeled out.

Sen. Ron Wyden (Ore.), the top Democrat on the panel, questioned why Republicans were rushing to pass a measure this week that was just having its first hearing — and one that he considered "a lemon."

"Nobody has to buy a lemon just because it's the last car on the lot," Wyden said.

[Cassidy on new health-care plan: ‘It’s not for Susan, it’s for the Mainers’]

The rush to rewrite the bill was so frenetic that Cassidy posted two separate bills on his website Monday morning. "The last version was just correcting drafting errors," he told the Finance Committee.

Unlike with earlier GOP proposals to repeal the ACA, Senate leaders have remained one step removed from the process this time. Asked whether any staffers outside his own had been involved in making changes to the bill over the weekend, Cassidy declined to answer.

While the figures in the revised draft aimed to ease the concerns of several key senators, there was no indication that the sponsors had abandoned their plan to make steep cuts to Medicaid through a per capita cap.

Such a move would reduce federal funding by billions of dollars by 2026 and would mean that even with a carve-out for Alaska elsewhere in the bill, the state may end up losing money. And other states would still be hit hard.

Graham, who spoke quickly and intensely in support of the bill's approach before the Senate panel Monday, said it reflected his trust in politicians who have more direct interaction with their constituents.

"My goal is to get the money and power out of Washington, closer to where people live," he said.

[In radio interview, Trump slams McCain, dings McConnell and botches a Senate candidate’s name]

But even Trump expressed skepticism Monday about the bill's chances of passage, blaming McCain and Collins for its expected demise in an interview on the "Rick & Bubba Show," an Alabama-based syndicated radio program.

McCain came out against the measure Friday, arguing that Republicans should work with Democrats to produce a bill that can attract wider support.

"You can call it what you want, but that's the only reason we don't have it, because of John McCain," Trump said of efforts to repeal the 2010 health-care law, adding later: "Looks like Susan Collins and some others will vote against. So we're going to lose two or three votes, and that's the end of that."

Democrats, for their part, continued to rail against the measure during the Senate hearing. Sen. Michael F. Bennet (D-Colo.) was especially animated during his remarks, raising his voice as he questioned the motivations of Republican senators.

"Why are we here, colleagues, making matters worse?" he asked.

[The Cassidy-Graham bill probably won’t become law. And more than half of America is good with that.]

Cruz made it clear over the weekend that he had grave reservations. On a Monday call with reporters, his aides said the senator had moved from yes to no after learning that the bill would not include the "consumer freedom" changes he had wanted from the start.

Republican leaders could call on Sen. Lamar Alexander (R-Tenn.) to revive negotiations with Sen. Patty Murray (D-Wash.) on a bipartisan package to stabilize the current insurance marketplaces. The pair had appeared to be reaching an agreement on a plan to guarantee subsidies to help cover out-of-pocket expenses for low-income people in exchange for limited waivers to give states more flexibility in how they spend that money. Those talks stalled when Alexander stepped aside to allow GOP leaders to focus on winning votes for Cassidy-Graham.

Many Republicans, however, oppose legislation to approve the subsidies without reforming the ACA insurance market.

"If you mean by 'fixing Obamacare' just dishing more money out to insurance companies, then no," Cornyn said.

Upon returning to the committee room Monday evening, Hatch declared that he would allow only one more round of questions given the Cass­idy-Graham bill's predicament.

"Let's face it, we're not getting anywhere," he remarked.

Amy Goldstein, David Weigel, Elise Viebeck and Paige Winfield Cunningham contributed to this report.

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