Inside Graham-Cassidy, the last minute push by Senate Republicans to resuscitate Obamacare repeal Everything you need to know on the new Republican health care plan.

 -- Congressional Republican efforts to repeal and replace Obamacare appeared to come to a standstill in July, after Sen. John McCain, R-Arizona., cast a "no" vote on the Senate floor, rejecting a bill backed by Senate Republican leadership.

Senate Majority Leader Mitch McConnell and Speaker of the House Paul Ryan suggested that week they would turn their attention to tax reform. But Monday those efforts to fulfill a signature campaign promise sprung back with considerable momentum as several lawmakers expressed support for a new repeal and replace bill, spearheaded by Sen. Lindsey Graham, R-S.C., and Sen. Bill Cassidy, R-La.

Introduced last week, Graham described the bill as Republicans’ last hope for rolling back President Barack Obama’s 2010 Affordable Care Act.

“If you believe repealing and replacing Obamacare is a good idea, this is your best and only chance to make it happen,” said Graham last week at a press conference.

The bill is also sponsored by Sen. Dean Heller, R-Nev., and Sen. Ron Johnson, R-Wis.

With 52 Republican Senators in Congress, the Graham-Cassidy bill can only afford to lose two Republican votes.

Here's what to know about the proposal:

The Graham-Cassidy plan

The Graham-Cassidy plan proposes distributing some federal funding currently available under the Affordable Care Act directly to states in the form of block grants. From 2020 to 2026, states would receive a set amount of federal funding to be used at their discretion for health care coverage, but cost-sharing subsidies the federal government pays to insurance companies to lower the cost of some plans on the individual insurance markets and money some states receives to expand their Medicaid rolls would go away.

The 31 states that applied for Medicaid expansion funding under the Affordable Care Act would see that money rolled back and eventually cut off. Graham and Cassidy say their plan would help balance Medicaid funding across the country, but Democrats say states with large Medicaid populations would struggle to provide coverage to their populations. Spending on Medicaid would be done per capita, meaning that less populous states like Maine and Alaska--home to two Senators currently on the fence about the plan--might struggle to foot the bill.

The plan would repeal two key parts of Obamacare, the individual and employer mandates, and states could apply for waives to alter what counts as an “essential health benefit” for insurance companies as they design their plan options. In addition, states could obtain waivers so that insurance companies could charge people with some pre-existing conditions more for some plans in their states. That practice is prohibited under current law. While insurers would likely still have to offer people with pre-existing plans choices, they could potentially limit coverage options as well under the proposed bill.

Graham-Cassidy would also allow people over the age of 30 to buy into catastrophic coverage plans, which have high deductibles but lower premiums and less benefits, as a way to get more healthy people covered. The bill would also allow insurance companies to charge older Americans five times more than younger Americans.

Obamacare taxes unpopular with Republicans, like the medical device tax, and tax on health savings accounts would also be repealed.

When will Congress vote?

McConnell assured Graham and Cassidy a vote would be scheduled with the condition that the Senators drum up the 50 votes needed to pass the bill. Republican leadership is hard at work trying to convince a small--but undecided--group to commit their support to the legislation.

McCain has raised procedural concerns over the bill, saying he is hesitant to support any legislation that has not been scrutinized in committee hearings.

“Why did -- why did Obamacare fail? Obamacare was rammed through with Democrats' votes only. Are we going to ram through our proposal with Democrats and the president? That's not the way to do it,” said McCain on CBS' "Face the Nation."

McCain is one of a handful of Senators, including Susan Collins, R-Maine, Lisa Murkowski, R-Alaska, Shelley Moore Capito, R. W.Va., and Rob Portman, R- Ohio, who have not indicated their support for the bill.

Some have appeared to scrap repeal efforts altogether in favor of working towards the small, bipartisan solutions for the individual insurance market that have been introduced in hearings with the Senate Health, Education, Labor and Pensions committee.

Sen. Rand Paul, R-Ky., has remained strongly opposed to the Graham-Cassidy bill, even calling it “Obamacare-lite.” With one Senator already voting no, Republicans cannot afford to lose more than one more vote.

A primary roadblock for Graham and Cassidy has been the Congressional Budget Office, or C.B.O. The C.B.O. announced on Monday that while it plans to offer a “preliminary assessment” of the bill, it will not be able to provide a full score of the bill for “at least a few weeks.” The C.B.O. score indicates how much the legislation will affect the government’s deficit and is needed for the Senate to vote.

Graham pleaded for the C.B.O. to expedite its scoring process so he can present cost estimates to Senate colleagues before Sept. 30. But Democrats say the Senate should not vote on the legislation unless a full--not preliminary--score is released.

The political battle ahead

Ryan called Graham-Cassidy, “our best, last chance to get repeal and replace" on Monday at an event in Wisconsin. And Republican leaders, sensing an opportunity to knock down key parts of Obamacare, are moving full speed ahead with the bill.

Republican Arizona Gov. Doug Ducey endorsed the bill on Monday, adding extra pressure for McCain to support a bill written by one of his closest allies and friends in the Senate.

In an interview with ABC News, Collins said she is still undecided. "I'm leaning no certainly, but I am still evaluating the bill and its text. We hadn't had it for very long and it's difficult to do without the assistance of the Congressional Budget Office."

Democrats say those cuts to Medicaid are unacceptable, with Sen. Chris Murphy, D-Ct., tweeting that Graham-Cassidy “is an intellectual and moral garbage truck fire.”

Planned Parenthood, which would face a one-year freeze on Medicaid funding, called it ”the worst ACA repeal bill yet.”