WASHINGTON — The simmering Senate debate over health care is about to go from shadowboxing to the real thing.

But even before Republicans roll out the details of their plan Thursday, Philadelphia-area senators made clear where they stand on the GOP's long-promised bill to repeal and replace the Affordable Care Act, often called Obamacare.

Pennsylvania Sen. Pat Toomey, the region's lone Republican, defended the GOP plan and its closed-door work crafting the bill. He said he expected the measure to include a version of his plan to scale back spending on Medicaid, the health program that provides coverage to millions of poor and disabled people.

The plan is part of a broader push to reshape a law that he blamed for raising costs and reducing consumer choices.

"What we've said for seven years now is that we want to repeal Obamacare, move health care in a different direction," Toomey said. "I think I'm going to be able to conclude that this is a big step in that direction."

Every Democrat from the region has vowed to oppose the measure, attacking it as a tax giveaway to the wealthy that would cut critical consumer protections.

"We have one choice: Stop the bill," Sen. Bob Casey of Pennsylvania said in a call with reporters this week. "It's as simple as that. This isn't a time for pretending that there's common ground on this bill."

At stake are health programs for the poor; safeguards for people with expensive preexisting medical conditions such as cancer; rules to ensure that certain services, such as maternity care, are covered; and an array of taxes and mandates underpinning the program, which has expanded health coverage for millions.

The overhaul represents one of President Trump's central promises and is his first major legislative initiative.

A vote could arrive as soon as next week.

Despite being one of 13 Republicans at the center of writing the Senate measure, Toomey said he had not seen all its details Wednesday, including the Medicaid provision he has pushed. But he argued that after years of debate over health care, a week of discussion on the GOP bill would be enough for him and others to understand the measure and make their cases.

"We're going to go over it over the course of the next week," Toomey said as reporters swarmed lawmakers close to the process. "We're going to argue about it, people will criticize it, praise it. It starts tomorrow morning."

He defended the GOP's methods.

"If we then tried to do an ordinary committee process, [Democrats] would have many, many opportunities to completely gum up the works indefinitely, which is their goal," he said. "That doesn't allow us to achieve what we promised the American people we'd do."

His plan for Medicaid has been a major flash point.

House Republicans called for capping Medicaid spending, a fundamental change to a program that now grows with demand. Toomey wants to go even further by using a less-generous calculation for inflation that would make the program grow more slowly each year. His idea would represent a win for fiscal conservatives worried about the deficit.

But several Republican senators from states that expanded Medicaid under the ACA want to go in the opposite direction and ease the House cuts, arguing that the program has helped millions in their states obtain health coverage.

Republicans can afford to lose only two votes from their 52-person caucus, and conservatives and moderates are pulling in opposite directions.

The bill's Medicaid reductions could cost Pennsylvania billions of dollars in federal aid, but Toomey argued that the program's spending has to slow for it to be viable.

Gov. Wolf said in a letter to Toomey that in practice, his plan would force care cuts as states face added costs.

Democrats charge that the GOP is trying to ram the bill through before anyone can figure out what it does. No public hearings have been held, or are expected.

"We're about to vote on a monumental bill within days and no one has seen it,"  Sen. Cory Booker (D., N.J.) said on a Facebook stream Tuesday as he and two colleagues visited the Congressional Budget Office to seek copies of the measure.

Republicans for years have attacked Democrats as using backroom deals and a Christmas Eve vote to advance the existing law — Toomey in 2010 said they had employed "every trick in the book."

But, Democrats countered this week that they also held weeks of public hearings and debated the measure on the Senate floor for 25 days, compared with the roughly one week planned by Republicans.

Even many in the GOP — from more moderate senators like Alaska's Lisa Murkowski to Utah conservative Mike Lee — have complained about being left in the dark.

Toomey said the issue has been discussed nearly every day within the GOP caucus, debated in public for years, and litigated in numerous elections — though he stopped short of promising to support the bill, saying he needed to see the specifics. "The details matter a lot," Toomey said. "We'll have them in the morning."