A last-ditch effort by Senate Republicans to repeal and replace ObamaCare is gaining steam, suggesting lawmakers could face another vote on ending the former president's signature law later this month.

Supporters do not have the 50 votes necessary to pass the bill yet, but pressure is growing on Republicans to back the measure, which could replace much of ObamaCare with block grants for states.

In a crucial boost for its chances on Monday, Arizona Gov. Doug Ducey (R) offered his support.

"Congress has 12 days to say 'yes' to Graham-Cassidy. It's time for them to get the job done," he said, referring to the bill's two main co-sponsors, Sens. Lindsey Graham (R-S.C.) and Bill Cassidy (R-La.).

Ducey's support is important because Sen. John McCain (R-Ariz.) has said the Arizona governor's position would be an important factor in how he votes.

McCain helped kill the repeal effort in July, calling for committee hearings and a bipartisan process, but he has left the door open to voting for Graham and Cassidy's bill.

Still, McCain on Monday criticized the rushed process leading up to a possible vote next week, while not ruling out voting for the bill.

"The governor of Arizona is favorably inclined, but I am going to have to have a lot more information," McCain said.

He reiterated his call for committee hearings and amendments, known as "regular order."

"We should be going through regular order," he said. "I've said that about 12 times."

Sen. Lisa Murkowski (R-Alaska), another crucial vote, also said Monday she is still studying the impacts on her state.

Senate GOP leadership is becoming more engaged. A source who has spoken to Senate Majority Leader Mitch McConnell's (R-Ky.) office described him as "taking it very seriously."

"The Leader asked CBO to prioritize the score on the legislation," said McConnell spokesman David Popp. "We expect regular staff briefings and Member discussions to continue."

Senate Majority Whip John Cornyn (R-Texas) last week said he is conducting a whip count to gauge the level of support for the bill, though he did not say he would be pushing for it.

A significant factor giving the measure new momentum is a fast-approaching Sept. 30 deadline.

At the end of the month, Republicans will not be able to use rules known as "budget reconciliation" to bypass a Democratic filibuster in the Senate.

If the measure can be filibustered, it has no chances of passing the Senate. As a result, Republicans are feeling pressure to move quickly to enact change they have long promised but have been unable to deliver, even with their party in control of Congress and the White House.

The last-ditch effort is expected to have the backing of most Republican senators, but there are some high-profile holdouts.

Sen. Rand Paul (R-Ky.) has been tweeting his opposition to the bill, saying it keeps too much of ObamaCare.

Sen. Susan Collins (R-Maine), who voted against previous repeal efforts, has also said she has concerns and is expected to be a no vote.

McCain has not endorsed the bill, though the fact that his close friend Graham is a co-sponsor has many observers thinking that he could be brought on board.

If McCain backs the bill and Paul maintains his opposition that could leave Murkowski as the deciding vote. Murkowski voted against every version of a repeal bill in July.

Murkowski told reporters Monday she is still studying the bill and its impact on Alaska.

"I need to figure out how all the numbers work with regards to Alaska," she said, noting she wanted to make sure there is enough money in the block grants for her state.

She also indicated she would prefer a separate, bipartisan approach that is currently being discussed in the Senate health committee, aimed at stabilizing ObamaCare.

"I always think that when you can get support for whatever the initiative from across the spectrum, it's just better legislation," she said.

Democrats are saying they are optimistic about those talks and a deal could be announced this week, and they are urging the GOP to go the bipartisan route, rather than back Cassidy-Graham.

"Conversations over the weekend were productive: the common ground has been staked out, the remaining differences are being negotiated, and the distance between the two sides on those issues is narrowing," Helen Hare, a spokeswoman for Democrats on the health committee, said in a statement.

The Congressional Budget Office said Monday that it would only have time to release a preliminary analysis of the Graham-Cassidy bill next week. That means lawmakers would be voting without a full analysis of the legislation's impact on premiums or how many people would lose coverage.

The Graham-Cassidy bill seeks to give more power to states by converting dollars currently spent on ObamaCare's subsidies and Medicaid expansion into a block grant to states.

Democrats argue the block grants would be too small and would lead to cuts to Medicaid and other health spending. The liberal Center on Budget and Policy Priorities found the bill would on average lead to a 17 percent cut in spending compared to ObamaCare in 2026.

The bill would also allow states to waive regulations protecting people with pre-existing conditions from being charged higher premiums, a provision that moderate Republicans have opposed in the past.

Jason Pye, vice president of legislative affairs at the conservative group FreedomWorks, said the bill is far from ideal, but better than doing nothing.

"It's better than the status quo so I think it's the last shot at doing something with 50 votes," he said.

Fifty votes would allow Vice President Mike Pence to cast a tie-breaking vote on the measure.

This story was last updated at 5:18 p.m.