(Bastien Inzaurralde/The Washington Post)

Senate Republicans are facing down an increasingly daunting challenge to secure the votes necessary to pass legislation to dramatically change President Barack Obama’s signature health-care law, and several senators said they would like more time to debate and tweak the plan as GOP leaders push for a vote this week.

At least five Republicans have already come out against their party’s bill — which can only afford to lose two votes — and over the weekend, more began expressing serious reservations and skepticism about the proposal.

The mounting dissatisfaction leaves Senate Republican leaders and the White House in a difficult position. In the coming days, moves to narrow the scope of the overhaul could appeal to moderates but anger conservatives, who believe the legislation does not go far enough to repeal and replace the Affordable Care Act, known as Obamacare.

A key moment will arrive early this week when the Congressional Budget Office releases an analysis of the bill that estimates how many people could lose coverage under the Republican plan, as well as what impact it might have on insurance premiums and how much money it could save the government.

The stalled Republican effort to pass a sweeping rewrite of the Affordable Care Act was further threatened Sunday when Republican senators from opposite sides of the party’s ideological spectrum voiced their disapproval, imperiling hopes for a Senate vote this week and President Trump’s chance to fulfill a core campaign pledge. 

What the Senate bill changes about Obamacare

Sen. Susan Collins (R-Maine) on Sunday expressed deep concerns about how the bill would cut expanded Medicaid funding for states, a key pillar of the Affordable Care Act that several centrists in the Senate are wary of rolling back, saying on ABC’s “This Week” that she worries about “what it means to our most vulnerable citizens.”

Collins also said she is concerned about the bill’s impact on the cost of insurance premiums and deductibles, especially for older Americans. 

“I’m going to look at the whole bill before making a decision,” she said, later adding, “It’s hard for me to see the bill passing this week.”

Underscoring the challenge facing Senate Majority Leader Mitch McConnell (R-Ky.), Sen. Rand Paul (R-Ky.), speaking on the same Sunday show, also voiced concerns with the bill — but for entirely different reasons.

Paul — who, along with fellow Republican Sens. Ted Cruz of Texas, Ron Johnson of Wisconsin and Mike Lee of Utah, has already said he cannot support the current bill — rejected the Republican plan as not fiscally austere enough but said that in the face of an impasse, he could support legislation that simply repeals Obama’s health-care law.

“I’ve been telling leadership for months now I’ll vote for a repeal,” Paul said. “And it doesn’t have to be a 100 percent repeal. So, for example, I’m for 100 percent repeal, that’s what I want. But if you give me 90 percent repeal, I’d probably vote for it. I might vote for 80 percent repeal.”

But simply repealing Obamacare or large parts of the law without making any other changes to the nation’s health-care system is not a realistic political possibility at the moment.

McConnell and his team remain convinced they must call a vote soon to avoid having health-care discussions dominate the summer, when they aim to move on to retooling tax legislation. In their circle, further talks are also seen as an opening for others to bolt.

“It’s not going to get any easier,” Senate Majority Whip John Cornyn (R-Tex.) told reporters on the sidelines of a three-day seminar organized by billionaire industrialist Charles Koch in Colorado Springs. “And, yes, I think August is the drop deadline, about August 1.”

As senators took to the airwaves Sunday, there were developments behind the scenes as GOP leaders made calls and worked to cobble together votes. But no firm decisions on vote-winning revisions were made.

There was new talk among key GOP figures about wooing moderates by altering the bill’s Medicaid changes, according to two people involved who would not speak publicly. By tweaking how federal funding is determined for Medicaid recipients and linking aspects to the medical component of the consumer price index, there is a belief that some moderates could be swayed, because they want assurances that funding would keep up with any rises in the cost of care, the people said.

Then would come the tightrope: If some senators can be persuaded to support revisions to the Medicaid portion of the bill, several conservatives are warning that unless their amendments are also included, they are unlikely to support the legislation. The hope is that a combination of those Medicaid changes and amendments from conservatives could pave the way to passage.

Progress in these conversations could postpone a vote for a couple weeks until after the Fourth of July holiday, the people said, but Senate leadership and the White House want to move this week if they can.

The administration itself, meanwhile, is sending mixed signals. An allied leadership PAC is launching an intensive advertising campaign against centrist Sen. Dean Heller (R-Nev.), a no vote, to pressure him to support the bill. On “This Week,” Kellyanne Conway, counselor to the president, said Trump “is working the phones, he’s having personal meetings, and he’s engaging with leaders.”

Still, the president’s own support for the legislation has at times been lukewarm. Over the weekend, he acknowledged he once called the initial Republican bill, which originated in the House, “mean” in a private meeting, but also urged senators on Twitter to pass it. 

Trump’s aides have seemed to signal that the White House is more likely to support the final Senate proposal over the original House bill going forward, and speaking this weekend on “Fox & Friends,” Trump said, “I want to see a bill with heart.”

Conway added that “the president and the White House are also open to getting Democratic votes,” and asked, “Why can’t we get a single Democrat to come to the table, to come to the White House, to speak to the president or anyone else about trying to improve a system that has not worked for everyone?”

But Democratic support seems unlikely. Senate Minority Leader Charles E. Schumer (D-N.Y.), speaking on “This Week,” said Democrats would only sit down with Republicans if they stop trying to repeal Obamacare. In an interview with The Washington Post, Sen. Bernie Sanders (I-Vt.) spoke of trying to postpone a vote on the bill to mount a stronger fight against it.

“One of the strategies is to just keep offering amendments, to delay this thing and delay this thing at least until after the July Fourth break,” Sanders said. “That would give us the opportunity to rally the American people in opposition to it. I think we should use every tactic that we can to delay this thing.” In fact — despite Trump’s campaign promise he would not cut Medicaid — the Senate bill includes deep cuts to projected spending on the program, deeper even than the House bill over the long run, and is expected to leave millions without or unable to afford health insurance.

On Sunday, there were attempts to tamp down criticism of the effect the Senate bill would have on Medicaid. Speaking on CBS’s “Face the Nation,” Sen. Patrick J. Toomey (R-Pa.), claimed the Republican plan “will codify and make permanent the Medicaid expansion,” and added, “No one loses coverage.” His comments echoed those by Conway, who told “This Week,” “These are not cuts to Medicaid.”

The legislation does not outright abolish the expansion of the program, under which 11 million Americans in 31 states have gained coverage since 2014. Instead, the bill would gradually eliminate the generous federal funding that has propped up the expansion, leaving states without enough money to pay for all their current beneficiaries.

Johnson, the senator from Wisconsin who surprised some fellow Republicans by co-signing a letter asking for more changes to the bill, said on NBC’s “Meet the Press” that there was no hurry to vote before the end of June.

“There’s no way we should be voting on this next week. No way,” Johnson said. “I have a hard time believing Wisconsin constituents or even myself will have enough time to properly evaluate this, for me to vote for a motion to proceed.”

At the same time, Johnson said he was not a pure “no” on the bill.

Sen. Bill Cassidy (R-La.), who criticized the secretive process by which the new bill was crafted and had preferred his own compromise to extend most of the Affordable Care Act, struck a similar tone on “Face the Nation.” After saying he was undecided, he clarified that small changes could win his vote.

“There are things in this bill that adversely affect my state that are peculiar to my state,” Cassidy said. “If those can be addressed, I will. If they can’t be addressed, I won’t. So right now, I am undecided.”

Progressive activists spent the weekend warning that Republicans such as Johnson and Cassidy could vote for the bill with minor tweaks. In Columbus, Ohio, at the second of three rallies Sanders and MoveOn.org organized to pressure swing-state Republican senators, MoveOn’s Washington director, Ben Wikler, warned a crowd of at least 1,000 activists that the protests of Senate Republicans might amount to nothing more than theatrical posturing.

“This is the week when Mitch McConnell and Republicans are going to introduce these tiny amendments and Republicans are going to say, ‘Oh, the bill is fixed! Oh, I can vote for it now!’ ” Wikler warned. “Are we going to let him get away with that?”

And looming over the discussions is another challenge: the Republican-controlled House, where any revised Senate bill would head and its ultimate fate would be decided. According to a White House official, Trump advisers are keeping in close touch with the conservative House Freedom Caucus — which helped tank the White House’s initial health-care push — as the Senate considers the bill, making sure that whatever ends up passing could pass muster with House conservatives.

David Weigel reported from Columbus, Ohio. James Hohmann in Colorado Springs contributed to this report.