(CNN) Republican senators departed Washington Tuesday with the fate of their last-ditch proposal to overhaul the Affordable Care Act still hanging in the balance.

The next few days will be critical for Graham-Cassidy, the latest GOP proposal to repeal and replace Obamacare. Even with members out, leadership, the bill's sponsors and the Trump administration are expected to go into overdrive to sell the legislation. Centers for Medicare and Medicaid Services Administrator Seema Verma will be available to answer questions and ply undecided members with analysis on how the bill would affect their states.

"People need information and that's why we're trying to provide them reliable information," said Senate Majority Whip John Cornyn.

Republican governors who have signed onto the legislation also are expected to play a role in courting undecideds.

"The conversations continue over the next few days," said South Dakota Republican Sen. John Thune, who specifically mentioned that Arizona Gov. Doug Ducey would play a role in trying to convince Arizona Sen. John McCain to come on board. "In the end, it's ultimately up to the leader."

The White House also will weigh in with President Donald Trump and Vice President Mike Pence making whatever phone calls they need to.

Progress on the bill

Graham-Cassidy has come a long way in a week. What began as a futile exercise to give Obamacare repeal one more try before the party's vehicle to pass it with 51 votes expires on September 30 has evolved into a serious opportunity for Republicans. But the rapid ascent of the bill has also made the last few days frantic for Republicans who are still trying to understand what it does. The Graham-Cassidy bill would eliminate federal funding for Medicaid expansion and for Obamacare subsidies that lower premiums, deductibles and co-pays in 2020. Instead, states would receive a lump sum of money annually through 2026.

Also, like the previous House and Senate repeal bills, it would sharply curtail federal support for the overall Medicaid program by sending states a fixed amount of funds based on enrollment or a lump sum.

Members are still trying to understand how the change would affect their states.

While members are away from Washington, they'll be crunching numbers. The Graham-Cassidy proposal through block grants would fundamentally reshape how much money each state receives from the federal government for Medicaid. There are winners and losers in the new formula -- and some members are trying to figure out which side of the equation they are on.

On Tuesday, Republican members met behind closed doors to discuss the latest proposal, which many have acknowledged they didn't even start sifting through until this weekend. Sen. John Kennedy of Louisiana described the lunch as a "lively" discussion. Another Republican member, who spoke on background in order to speak freely, described the hour-long meeting as "very upbeat," with Vice President Mike Pence encouraging members that if they could pass the proposal, it had a real shot in the House.

The bill's sponsors, Sen. Lindsey Graham of South Carolina and Bill Cassidy of Louisiana, also spoke out and cast their plan as a case for state's rights.

Potential "no" votes

Not everyone's reaction to the lunch was quite so positive, however. It was clear that Tuesday did not provide Republican leadership with the definitive green light they needed to announce they were bringing the health care bill to the floor.

Sen. Susan Collins of Maine, who had already expressed serious concerns about Graham-Cassidy, went even further Tuesday, suggesting that the new proposal may be even more harmful than the previous one.

The bill, she told CNN, would restructure Medicaid in a fundamental way without carefully considering the ramifications, costing her state around $1 billion in funding over a decade. Another cause for concern: People with pre-existing conditions would be hurt.

Graham-Cassidy "seems to have many of the same flaws of the bill we rejected previously, and in fact, it has some additional flaws because there's some language that leads me to believe that people worth preexisting conditions would not be protected in some states," Collins said.

It didn't help that there would be no comprehensive analysis from the Congressional Budget Office before next week, she added.

Sen. Lisa Murkowski of Alaska also said the gathering did not help alleviate her concerns.

Speaking to reporters moments after the governor of her state, Bill Walker, came out against Graham-Cassidy, Murkowski made clear that the governor's opposition would weigh on her heavily.

"I have reminded him that it is one thing for us here in Washington, D.C., to figure out formulas, (but) as a governor, he is the one who implements them," Murkowksi said. "So I want his input. I have had a couple of different calls with him and I think that's been beneficial."

McCain was less forthcoming with reporters Tuesday about his own deliberation about Graham-Cassidy. But he made clear he was less than pleased that another partisan bill was gaining momentum.

Asked about the Senate finance committee's decision to hold a last-minute hearing on Graham-Cassidy next week, McCain sarcastically responded, "I'm glad to hear that. That's wonderful news. Ta-da!" before proceeding to play an imaginary trumpet with his fingers.

Pressed on whether one hearing counts as "regular order," McCain quipped at a CNN reporter: "Do you think that that's regular order?"

"I always thought regular order was hearings and debates and amendments and into the floor with debates and discussion and amendments! That's what I thought regular order was," McCain said.

The bottom line for leadership is they only need 50 votes to finally repeal and replace Obamacare, and they are as close as they've ever been to getting there.

But time away from Washington is an unpredictable factor, and it's not clear that the three members on the fence are going to be able to be persuaded in that time.

The problem for a handful of members is that reversing their "no" vote from July and voting "yes" on Graham-Cassidy would force them to publicly agree to provisions and a process they once decried.