Senate leaders released a slightly revised version of theirhealth care bill Monday as Senate Majority Leader MitchMcConnell tries to win over enough holdouts to pass themeasure, with at least six Republicans signaling opposition.

Related: Cornyn expects to move ahead on Senate health billWednesday

The most significant change is the inclusion of a new provisionto encourage Americans to maintain continuous health care coveragethat would replace Obamacare’s individual mandate. The newprovision would impose a six-month waiting period before newinsurance goes into effect for anyone who had a break in coveragelasting 63 days or longer in the prior year. It would takeeffect beginning in 2019.

A number of Republican senators are still demanding a variety ofchanges in what is shaping up as McConnell’s toughest test asSenate majority leader.

McConnell can only afford two defections and still pass hisObamacare repeal legislation, but Republicans only saw McConnell’sdraft bill for the first time Thursday. With both moderates andconservatives expressing deep concern about McConnell’s "discussiondraft," he faces a narrow path to passage.

Defeat may scuttle plans to replace Obamacare for theforeseeable future.

“It will hurt the Republicans if they fumble on the issue thathas been their signature issue," said Julian Zelizer, an historianat Princeton University. "That won’t look good if they can’t dothis. This is a high-stakes moment.”

Related: Four GOP senators spurn health plan aimed atunifying party

And for McConnell, it will show whether he can move beyond hisreputation as an obstructionist and deliver on his party’s biggestpriorities.

The health care measure could dramatically affect manyAmericans’ health and financial security while also posingchallenges to state governments facing proposed cuts in Medicaidcoverage for low-income residents.

Related: How killing Obamacare might save some of Obamacare,for a while

McConnell’s challenge is similar to the one Speaker Paul Ryanfaced when the House passed its own plan in May -- conservative andmoderate GOP wings balking at different parts -- but with a muchsmaller margin of error to pass his version of the plan, H.R. 1628.With 50 votes, a tie-breaker by Vice President Mike Pence wouldensure passage.

Nevada Senator Dean Heller said Friday he’ll oppose the bill inits current form largely because of its cuts to Medicaid and tosubsidies for individual insurance coverage. Heller, the SenateRepublican seen as most at risk in the 2018 midterm election, alsosaid he’s likely to vote with Democrats to block it from floorconsideration.

On Sunday’s television talk shows, two other moderates -- SusanCollins of Maine and Bill Cassidy of Louisiana -- said they can’tsay yet how they’ll vote and expressed reservations aboutMcConnell’s speedy deadline for action.

Collins said she’s "very concerned" about the bill’s impact onMedicaid coverage for the sickest people. She also opposes itsone-year ban on funding for Planned Parenthood, a provision shewants to strike on the Senate floor.

"It’s hard for me to see the bill passing this week, but that’sup to the majority leader," Collins said on ABC’s "This Week."

Conversely, four conservatives -- Rand Paul of Kentucky, TedCruz of Texas, Mike Lee of Utah and Ron Johnson of Wisconsin -- saythe plan keeps too much of Obamacare. They announced they’ll need anumber of changes before they’ll back it, and Johnson said Sundaythe rushed process could cause him to join Heller in voting toblock the start of debate.

"I have a hard time believing Wisconsin constituents, or evenmyself, will have enough time to properly evaluate this for me tovote for the motion to proceed," he said on NBC’s "Meet thePress."

The Congressional Budget Office will issue an analysis as earlyas Monday spelling out how many Americans may lose health insuranceunder the bill and whether it contains enough financial wiggle roomto let McConnell try to woo holdout senators with increasedfunds.

Related: AHCA continues to bring out thecritics

The CBO said the House version, which includes $834 billion inMedicaid cuts and $664 billion in tax cuts, would cause 23 millionAmericans to lose their health insurance by 2026. A reduction inthe number of people losing insurance under the Senate bill mightbolster support for it.

‘Vote-a-rama’

After talks with lawmakers, McConnell will probably introduce arevised bill in the Senate Tuesday evening, said Senator JohnCornyn of Texas, the No. 2 Republican leader. That would set off a20-hour debate later in the week, followed by an all-night“vote-a-rama” to consider potentially hundreds of amendments --including many designed by Democrats to be political booby traps --before a final vote early Friday morning.

Related: Senate GOP health bill to break with House on keypoints

While some senators have been "more public about their concerns"with the measure, "they want to get to yes," Cornyn told reportersSunday at a Koch Brothers donor gathering in Colorado Springs,Colorado.

Senator Richard Burr of North Carolina, the IntelligenceCommittee chairman and a McConnell ally, went from doubting whetherthe Senate could get a bill done this year to predictingpassage.

"A few weeks ago I said it was difficult for me to see how itgets done. And I came back, and they pulled the Band-Aid off andnow it’s going to get done," Burr said.

The showdown may get delayed until after next week’s July 4recess, though, because some senators -- including Johnson -- areseeking more time to examine the measure.

Cruz’s demands

Cruz was ready Thursday with a list of changes he’s demanding,which included letting states design coverage without needingfederal waivers, allowing consumers to buy insurance across statelines, and allowing insurers that meet federal mandates to sellother plans that don’t comply.

Other senators also want revisions. Rob Portman of Ohio said thebill’s $2 billion to combat opioid addiction isn’t nearly enough.Alaska’s Lisa Murkowski joined Collins in expressing concern aboutthe one-year ban on funds for Planned Parenthood.

The new bill made relatively modest changes to the measure thatpassed the House last month.

Senate leaders added funds in the first few years aimed atbringing down insurance premiums and shoring up Obamacaremarketplaces. An extra $62 billion over eight years would go to astate innovation fund, which can be used for coverage for high-riskpatients, reinsurance and other items.

Austerity push

To appeal to conservatives, the Senate plan would imposelonger-term austerity on health spending. In 2025, it would gofurther than the House in capping federal Medicaid funds by usingthe consumer price index, rather than a measure of medicalinflation that tends to rise more quickly.

Related: 5 things for agents to know about the Senate healthbill

Over time, the extra help for states and the insurance exchangeswould phase out, and cuts to Medicaid and to insurance protectionswould phase in.

While the bill provides far more assistance to the poor andnear-poor than the House bill, it’s still substantially lessgenerous overall than the Affordable Care Act. The biggest loserswould be people at 351 percent of the federal poverty level -- alittle over $42,000 for an individual -- who would go from paying amaximum 9.7 percent of their income in premiums to having no cap atall.

The Senate also keeps almost all of the House’s tax cuts intact-- allowing Democrats to argue that the measure finances tax cutsfor the wealthy with reductions in health care for otherpeople.

McConnell has flexed significant partisan muscle even beforestarting work on the health plan. In April, he ignited the “nuclearoption” to confirm President Donald Trump’s Supreme Court nominee,Neil Gorsuch, changing Senate rules permanently to bar filibustersof high-court picks. Last year, McConnell refused to considerformer President Barack Obama’s nominee, Merrick Garland, gamblingsuccessfully that a Republican would win the presidency and get tofill the seat.

The majority leader is taking heat from Democrats and many inhis own party for secretly drafting the health bill with a smallgroup of congressional aides. It isn’t clear how much that hurtshis chances of replacing Obamacare, but there is some risk otherswill join Heller and vote with Democrats to blockconsideration.

"We don’t have enough information -- I don’t have the feedbackfrom constituencies who will not have had enough time to review theSenate bill," Johnson said Sunday. "We should not be voting on thisnext week."

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