Washington • The floundering Republican attempt to undo the Affordable Care Act met hardening resistance from key GOP senators Sunday that left it on the verge of collapse even as advocates vowed to keep pushing for a vote this week.

With party leaders just one “no” vote away from defeat, Republican senators from across the political spectrum distanced themselves from the plan written by Sens. Bill Cassidy, R-La., and Lindsey Graham, R-S.C. They voiced opinions ranging from measured skepticism to outright hostility toward a proposal that was already trending toward failure over the last three days.

The fresh discord over a signature Republican promise added turbulence to the start of a critical week for President Donald Trump and Senate Majority Leader Mitch McConnell, R-Ky. In addition to health care, both are watching Tuesday’s special election primary runoff in Alabama, a high-stakes intraparty fight between establishment Republicans and conservatives that could set the tone for the midterm elections next year. GOP leaders are also expected to unveil their most detailed blueprint yet of tax cuts they hope to pass by the end of the year.

Sen. Susan Collins, R-Maine, a moderate Republican who has opposed previous efforts that cut Medicaid and lifted coverage requirements, said in a TV interview that it was “very difficult” to envision voting for the health care bill.

Sen. Ted Cruz, R-Texas, a conservative who has advocated for a more far-reaching repeal of Obamacare, said he and at least one other colleague do not back the measure “right now.”

And Sen. Rand Paul, R-Ky., who has stated definitively that he opposes the current measure, showed no signs of backing down absent dramatic changes to the bill’s core approach that likely would come at the cost of other Republican votes.

Graham and Cassidy pledged to keep trying to pass their bill — but the White House and McConnell gave differing accounts of the path ahead. White House legislative affairs director Marc Short predicted a Wednesday vote, while a McConnell spokesman declined to publicly embrace that timeline.

Speaking on CNN’s “State of the Union,” Collins cited concerns about how the Cassidy-Graham legislation would affect Medicaid recipients and people with preexisting medical conditions, among other things.

“It is very difficult for me to envision a scenario where I would end up voting for this bill,” Collins said. “I have a number of serious reservations about it.”

Collins voted against a July repeal bill and is a key swing vote in the current dynamic. She said she chatted at length with Vice President Mike Pence on Saturday, but it wasn’t enough to sway her. She said she wants to see the limited analysis due out this week from the nonpartisan Congressional Budget Office before she makes a final decision.

Two Republican senators — Paul and John McCain, Ariz. — have already said they would vote against Cassidy-Graham. A third would be enough to defeat the bill, since no Democrats are expected to support it. Republicans hold a 52-48 advantage in the Senate and can lose only two of their own and still pass legislation with the help of a tiebreaking vote from Pence.

The bill has been roundly rejected by influential national groups representing physicians, hospitals and insurers. Over the weekend, six such organizations, including the American Medical Association and American Hospital Association, issued a joint statement urging the Senate to reject it.

While the CBO plans to release a “preliminary assessment” early this week, officials there have said they will not be able to provide estimates of how Cassidy-Graham would affect insurance premiums or the number of people with coverage “for at least several weeks.” Trump and McConnell are trying to bring the bill to a vote by the end of this week to take advantage of a procedural rule allowing the plan to pass with just 51 votes.

It remained far from clear Sunday that they could get even close to that number.

Addressing Cassidy-Graham at the Texas Tribune Festival in Austin, Cruz said: “Right now, they don’t have my vote. And I don’t think they have Mike Lee’s either,” referring to one of Utah’s senators and a fellow conservative.

Cruz said that he and Lee met with Graham and Cassidy last week to propose changes to the measure that would get them to yes. Their changes were not included in the latest draft.

Conn Carroll, a Lee spokesman, said Sunday: “We want some technical changes. We are working with Cassidy, but we haven’t committed to anything yet.”

Graham and Cassidy appeared on ABC’s “This Week with George Stephanopoulos,” where they defended their plan and vowed to keep up their efforts to shepherd it to passage.

“We’re moving forward. And we’ll see what happens next week. I’m very excited about it,” Graham said. The South Carolina Republican mentioned Collins and Paul as he made his pitch.

“Rand Paul objects to the taxes,” he said. “But when you look at the bill, Rand, we save a lot of money over time for Medicaid. We put a cap on Obamacare growth.”

Paul said in a Sunday interview that he broadly opposes a keystone of the Cassidy-Graham plan: turning funding for the ACA into block grants for states.

“The problem I have with block grants is that looks like I’ve affirmatively said I’m OK with 90 percent of Obamacare as long as we reshuffle it and give it to Republican states,” he said. “That’s a horrible message.”

Paul said he is willing to hear out suggestions about how that element of the bill could be constricted. “Would I talk to them if they said they wanted to make the block grants half as much? I might,” he said.

Paul presents another challenge as well: Winning him over would likely alienate other Republican senators who oppose a more aggressive repeal. That left GOP leaders no better off in their quest to secure enough Republican votes to pass Cassidy-Graham.

The proposal, which would also dramatically cut Medicaid spending over time, has drawn concerns from Republicans from states that have expanded Medicaid under the ACA. In an interview on CBS’ “Face The Nation,” Sen. Cory Gardner, R-Colo., whose state expanded Medicaid, said he needs more information before he’ll take a position.

“I think the CBO will have a role to play in this,” Gardner said. “I believe there’s information that will be coming through a committee hearing on Monday and additional text changes that will add additional information.”

McConnell is also keeping a close eye this week on the Senate race in Alabama, where Republican Sen. Luther Strange is trying to get past insurgent primary challenger Roy Moore, a controversial but popular former judge. Trump and McConnell both back Strange, but supporters and associates of Trump, including former chief strategist Stephen Bannon and Housing and Urban Development Secretary Ben Carson, have praised Moore.

A Moore victory would be a blow to both McConnell and Trump, who have rallied their powerful political operations behind Strange. Some Republicans also believe that outcome would embolden other conservative insurgents to challenge Republican senators in 2018.

Also this week, the “Big Six” negotiators from the White House, Senate and House are expected to unveil more details of their tax reform plan, which like the health care talks could spark messy disagreements among Republicans.

Some of the elements of the plan have already started to take shape. Republicans are targeting a corporate rate of 20 percent in their overhaul, according to three people familiar with the emerging blueprint — a number that represents a substantial cut from the current 35 percent rate but falls short of the 15 percent Trump has advocated.

But for Senate Republicans, the first order of business this week is resolving the health care push one way or the other. Even the bill’s champions have already started pondering the prospect of failure.

Asked on “This Week” what he will tell people if he comes up short, Graham responded: “That I did everything I could to get money and power out of Washington to give you better health care closer to where you live, and I’m not going to stop fighting.”

He also held up the possibility of using health care as a negotiating tactic in future legislative talks.

“I’m on the Budget Committee,” he said, adding, “we’re not going to vote for a budget resolution that doesn’t allow the health care debate to continue.”

——

The Washington Post’s Robert Costa and Carol Morello contributed to this report.