By Robert Pear & Thomas Kaplan, New York Times–

Senate Republican leaders scrambled Sunday to rally support for their health care bill as opposition continued to build inside and outside Congress, and as several Republican senators questioned whether it would be approved this week.

President Trump expressed confidence that the bill to repeal the guts of the Affordable Care Act would pass.

“Health care is a very, very tough thing to get,” Mr. Trump said in an interview shown Sunday on Fox News. “But I think we’re going to get it. We don’t have too much of a choice because the alternative is the dead carcass of Obamacare.”

With Democrats solidly opposed to the legislation, Senate Republicans must find the votes from within. They can afford to lose only two votes, but five Republican senators have announced that they cannot support the health care bill as drafted, and others have expressed concerns.

Senate leaders have been trying to lock down Republican votes by funneling money to red states, engineering a special deal for Alaska and arguing that they could insure more people at a lower cost than the House, which passed a repeal bill last month.

But as more analysis of the bill reached state officials, especially in places that expanded Medicaid access under the Affordable Care Act, misgivings grew. Senator Bill Cassidy, a Louisiana Republican and doctor who is considered a critical vote, said he remained undecided. Louisiana, with its high levels of poverty, recently expanded Medicaid.

“There are things in this bill which adversely affect my state, that are peculiar to my state,” Mr. Cassidy said on CBS’s “Face the Nation.”

The bill was drafted in secret, mainly by the Senate majority leader, Mitch McConnell of Kentucky, who unveiled it on Thursday. Mr. McConnell wants a vote this week, before lawmakers take a break for the Fourth of July holiday.

Senator Jerry Moran of Kansas, usually a reliable vote for Senate Republican leaders, said on Fox News, “I just don’t know whether the votes will be there by the end of the week.”

Over the weekend, senators and their aides were poring over the bill, drafting possible amendments, preparing speeches and compiling personal stories from constituents whom they portrayed as either beneficiaries or victims of the Affordable Care Act.

But the bill’s supporters were battling an internal threat: reluctant Republicans. Senator Ron Johnson of Wisconsin said Sunday that “there’s no way we should be voting” on the legislation this week. “No way.”

“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,” Mr. Johnson said on NBC’s “Meet the Press.”

And Senator Susan Collins, Republican of Maine, said on ABC’s “This Week”: “It’s hard for me to see the bill passing this week, but that’s up to the majority leader. We could well be in all night a couple of nights.”

The U.S. Chamber of Commerce, the National Federation of Independent Business and the National Retail Federation have all said they support the bill. Thomas J. Donohue, the president of the Chamber of Commerce, said it would “help stabilize crumbling insurance markets” and eliminate “ill-conceived Washington mandates and taxes.”

But much of the nation’s $3 trillion health care industry opposes the bill. And Mr. McConnell has done little to woo the health care stakeholders whom Mr. Obama courted assiduously from his first months in office.

The concerns expressed by outside groups also appear to be growing. Top lieutenants in Charles G. and David H. Koch’s political network sharply criticized the legislation over the weekend, saying it was insufficiently conservative and did not do enough to rein in the growth of Medicaid. And a number of Republican governors have joined doctors, hospitals and patient advocacy groups in opposing the bill, in part because of its cuts to Medicaid.

Mr. McConnell has only a few days to wheel, deal and cajole reluctant senators to get behind legislation that has grown less popular with more exposure. He has considerable firepower to win votes by guaranteeing amendments that would address the concerns of individual Republican senators, and by playing on their loyalty to him and to conservative voters still demanding an end to the Affordable Care Act. At the same time, Democrats say, he has striking liabilities. Mr. Trump has endorsed the bill, and Democrats say they will take every opportunity to link the legislation to an unpopular president.

And the Democratic wall of opposition is backed by less partisan voices. Senators are being flooded with appeals like this from the advocacy arm of the American Cancer Society: “Cancer is scary enough. Don’t take away our coverage.”

The American Childhood Cancer Organization, a charitable group formed by parents, is mobilizing a small army of grass-roots lobbyists with the message that the bill, with its deep cuts to Medicaid, “will threaten the lives of children battling cancer.”

The United States Conference of Catholic Bishops said the Senate bill was “unacceptable as written” and would “wreak havoc on low-income families.” At the same time, the bishops said they liked two sections that seek to “prohibit the use of taxpayer funds to pay for abortion or plans that cover it.”

Republicans are finding allies to be few and inconstant. Mr. Trump has said he is “very supportive” of the Senate bill. But that support will be of limited help to Mr. McConnell. Few senators feel loyal to Mr. Trump, whose erratic message has often weakened his influence on Capitol Hill.

After pushing for passage of the House repeal bill, he criticized it as “mean” several weeks later. A spokeswoman, Sarah Huckabee Sanders, said last week that Mr. Trump did not necessarily support cuts to Medicaid, even though his budget and the Senate bill would make such cuts.

Kellyanne Conway, a top adviser to Mr. Trump, claimed on Sunday that the Senate bill did not actually cut Medicaid. Ms. Collins said, “I respectfully disagree with her analysis.”

So far, five Republican senators have announced that they cannot support the bill as drafted: Dean Heller of Nevada, who says it cuts coverage too deeply, and four conservatives — Rand Paul of Kentucky, Ted Cruz of Texas, Mike Lee of Utah and Mr. Johnson — who say it does not do enough to lower health costs. Other Republicans, like Ms. Collins and Senator Lisa Murkowski of Alaska, have expressed misgivings, and Senator Ben Sasse of Nebraska declined to say Sunday how he would vote.

Senate leaders, trying to muster support, are looking for ways to address a conspicuous omission: The bill requires insurers to accept anyone who applies, but repeals the mandate for people to have coverage and does not replace it with anything. So people could wait and buy insurance only when they need it. Insurers say they need large numbers of healthy people to help pay for those who are sick.

Republicans said they might revise their bill to establish a six-month waiting period for people who go without insurance and then want to sign up, in the belief that this would encourage consumers to maintain continuous coverage.

The House bill has an incentive, imposing a 30 percent surcharge on premiums for people who have gone without insurance. But the Congressional Budget Office said this provision could backfire. As a result of the surcharge, it said, two million fewer people would enroll, and the people most likely to be deterred are those who are healthy.

The Senate’s answer also has potential problems. For someone with cancer, a six-month waiting period could be a death sentence.

The Senate fight is happening amid a striking shift in public opinion. Fifty-one percent of Americans now have favorable views of the Affordable Care Act, according to a monthly tracking poll by the Kaiser Family Foundation. “That’s the first time in our 79 tracking polls over seven years that this share has topped 50 percent,” said Craig Palosky, a spokesman for the foundation.

Medicaid is by far the largest program of federal grants to the states, and state officials are always trying to tweak the formula for distributing that money to their advantage.

The House and Senate bills would convert Medicaid from an open-ended entitlement program to a system of per-capita payments for beneficiaries. A novel feature of the Senate bill would redistribute federal Medicaid money from higher-spending states like New York to lower-spending states like Alabama.

One noteworthy exception to this provision is tailor-made for Alaska. “This paragraph shall not apply to any state that has a population density of less than 15 individuals per square mile,” it says.

Only five states — Alaska, Montana, North Dakota, South Dakota and Wyoming — meet that criterion, and Alaska’s two Republican senators have expressed concern about the bill’s potential effects on their state, where medical costs are exceptionally high.

Ms. Murkowski said federal legislation must recognize Alaska’s high costs. Premiums on the insurance exchange there average about $1,000 a month for an individual, according to federal data. But the special provision may not be enough to win Ms. Murkowski’s vote. She is also concerned about two other sections of the bill: one that would cut federal funds for the expansion of Medicaid under the Affordable Care Act and one that would block federal Medicaid payments to Planned Parenthood.

Get politics and Washington news updates via Facebook, Twitter and in the Morning Briefing newsletter.