WASHINGTON — Pitching Republicans' “last shot” to fulfill pledges to replace Obamacare, Louisiana’s Bill Cassidy and three U.S. Senate colleagues rolled out a sweeping healthcare plan Wednesday, just 17 days ahead of a deadline for a vote.

U.S. Sen. Lindsey Graham, R-South Carolina, the plan's lead author, took jabs at his party's leaders — the White House has been largely quiet on the proposal and Senate Republican leaders have left it up to the gang backing the bill to drum up the needed votes — amid pleas for support.

“The only thing stopping us from having this idea debated on the floor of the United States Senate is lack of leadership,” Graham said.

Graham, Cassidy and co-sponsors U.S. Sens. Dean Heller of Nevada and Ron Johnson of Wisconsin also described their bill as the only alternative to proposals for national single-payer health insurance that have quickly gained traction among Democrats.

"Behind me is the only thing between you and single-payer healthcare — a small band of brothers searching for a sister," Graham quipped at a news conference, gesturing at Heller, Johnson, Cassidy and former Sen. Rick Santorum, R-Pennsylvania, who's been lobbying on behalf of the bill.

"Liberals will fight like tigers to the bitter end to get what they want," Graham added.

U.S. Sen. Bernie Sanders, an independent from Vermont who ran an insurgent populist campaign for the Democratic presidential nomination last year, also picked Wednesday to unveil his own, very different health insurance proposal, a generous government-backed initiative billed as "Medicare-for-all."

Conservatives have described a single-payer insurance plan like Sanders' proposal in grim terms, labeling it a massive government takeover of the country's healthcare system that would strangle out individual choice.

Cassidy, a physician and Baton Rouge Republican who's devoted long hours to hammering out an alternative to Obamacare, walked reporters through the team's proposal, including a revamped funding formula to divvy up federal money between states.

The plan centers around block-granting billions of dollars in Obamacare taxes that currently fund states' Medicaid expansions and individual health insurance subsidies. The money would be funneled through the popular Children's Health Insurance Program, or CHIP, a long-standing block grant to provide care for low- and moderate-income children.

The bill's formula would generally redistribute money away from states that expanded Medicaid under Obamacare and spread them across the country, boosting the amount of federal money headed to states — largely controlled by Republicans — that refused to expand Medicaid.

Cassidy, in rejecting criticism of the proposal as "partisan," said Democratic senators from purple states where Republican governors or legislatures blocked Medicaid expansion — a list that includes Virginia, Wisconsin and Indiana — should back the plan because of the increased money.

Louisiana Gov. John Bel Edwards, a Democrat, expanded Medicaid in the state in 2016, shortly after taking office. Edwards' predecessor, Bobby Jindal, had opposed expanding the program.

A spokesman for Edwards did not respond to requests for comment about the proposal.

Cassidy has said if the proposal became law Louisiana would come out "about even" in terms of federal dollars compared to the amount the state currently receives.

The Congressional Budget Office has not yet scored the bill. The Center on Budget and Policy Priorities, a liberal D.C.-based think tank, concluded Wednesday that Louisiana would lose about $3.2 billion in federal funding over the next decade when compared to current law, under which federal spending on healthcare is set to increase.

Graham described ballooning future Medicaid costs as unsustainable for the federal budget. Cassidy has previously described the program as a potential “black hole” for tax dollars that could squeeze out other budget priorities.

Opponents, though, see the cap on Medicaid growth in this plan and others as a dangerous and deep gash in a critical social program. The cap means the federal government would set aside far less on healthcare than under current law — the Center on Budget and Policy Priorities estimated the figure at about $80 billion over the next decade — and wouldn't increase with the rising costs of healthcare.

The wide-ranging freedom offered to states under the law is, according to Cassidy, one of its biggest selling points. The block grants would come with relatively few restrictions, meaning states could use the money to fund a range of health insurance-related initiatives, from subsidizing employer-provided plans to keeping their Obamacare exchanges running.

The flexibility would shift decision-making on healthcare from Washington, D.C., to state capitals, the proposal’s backers argued Wednesday, allowing different states to craft radically different solutions.

But that flexibility is simultaneously one of the biggest concerns of critics of the proposals. States could potentially waive key requirements in the Affordable Care Act that forced insurers to charge everyone the same price, regardless of prior health conditions. The bill also doesn't require states to use the money on healthcare for low-income residents, meaning states could potentially shift dollars away from the poor and toward those with higher incomes.

For those who buy their health insurance on the Affordable Care Act's individual exchanges and receive subsidies, any future subsidies would depend on how states deploy the block grants. Some states would almost certainly redirect the money to other programs, creating uncertainty for the future of the individual markets.

For states that want to keep the Obamacare exchanges and Medicaid expansion running — a local option that Cassidy has repeatedly touted — the limits on future growth in funding would mean pumping far more state money into the programs.

“Many millions of Americans would lose their health care coverage and many more would have worse or more expensive plans,” said Aviva Aron-Dine, a senior fellow at the Center on Budget and Policy Priorities who held a senior role in the Obama administration.

Groups opposed to the plan also blasted it for gutting funding for Planned Parenthood and for the rushed timeline.

“This last-ditch effort is just another ACA repeal bill that would have the same devastating effects as previous bills that Congress rejected,” said Jan Moller, executive director of the Louisiana Budget Project, which advocates for low- and moderate-income state residents. “Just like the earlier failed efforts, this latest bill would take away coverage from millions of people, end the Medicaid expansion, raise costs for consumers and gut the Medicaid program as we know it.”

Cassidy acknowledged that any Democratic support for the bill was highly unlikely. Cassidy said he's had discussions with Edwards about the law but didn't anticipate the endorsement of the governor — or any other Democratic governors or U.S. senators.

Because of the Republican Party's narrow 52-seat majority in the Senate, the bill needs near-unanimous support to pass. It also faces a looming September 30 deadline to pass on a party-line, simple-majority vote under a procedure known as reconciliation. After that date, the plan would require 60 votes to pass, a near impossibility given unified Democratic opposition.

A number of Senate Republicans have expressed skepticism about the Graham-Cassidy-Heller-Johnson proposal, most suggesting the looming deadline makes passage unlikely and that the party has moved on to other priorities, including tax reform.

But Graham, Cassidy, Heller and Johnson all implored their colleagues to join their fight. In doing so, Graham and others criticized top national leaders of their party — President Donald Trump and Senate Majority Leader Mitch McConnell in particular — for not putting their political muscle behind the bill.

McConnell has declined to back the idea, calling the path forward on healthcare “unclear” on Tuesday and saying he’s also open to a bipartisan effort — led by U.S. Sens. Lamar Alexander, R-Tennessee, and Patty Murray, D-Washington — to shore up the Obamacare exchanges.

U.S. Sen. Orrin Hatch, R-Utah, responded with a blunt “no” when asked by reporters Monday whether he anticipates a vote on the bill. Hatch is the chairman of the Senate finance committee, one of two committees which would normally hold hearings on the bill. The chairman of the other, Tennessee’s Alexander, is heading up the bipartisan effort to shore up the exchanges.

But Johnson guaranteed the bill would get a committee hearing — even if other Republican colleagues like Hatch and Alexander didn’t sign on — by slotting it for a hearing in the Senate’s homeland security committee. Johnson is chairman of that committee.

Trump, meanwhile, has sent mixed messages on whether he wants to forge forward with healthcare legislation, tweeting last Friday, “Republicans, sorry, but I've been hearing about Repeal & Replace for 7 years, didn't happen!”

Graham urged the president to “pick up the phone” to push Republicans senators and governors to back the bill. In a written statement, Trump “applauded” Cassidy and Graham for continuing to work on repealing Obamacare.

“As I have continued to say, inaction is not an option, and I sincerely hope that Senators Graham and Cassidy have found a way to address the Obamacare crisis,” the president said.

Absent from the statement, however, was an explicit endorsement of the plan or a pledge to push for its passage.

Advocate staff write Rebekah Allen contributed to this story.

Follow Bryn Stole on Twitter, @BrynStole.