WASHINGTON -- For years, Republicans have run passionate campaigns vowing to repeal the Affordable Care Act. But with a GOP-authored bill targeting the law now in front of them and backed by President Trump, congressional Republicans were treading cautiously Tuesday.

GOP lawmakers from the Philadelphia region said they were still reviewing the plan unveiled Monday night, neither supporting nor opposing a measure that could finally reshape the country's health system to match Republicans' vision and roll back much of what is widely called Obamacare.

Sen. Pat Toomey (R., Pa.) said he was still combing through the 123-page measure: "I haven't made a decision yet."

Rep. Tom MacArthur (R., N.J.) told a town hall audience Monday night that he was unsure how he would vote. He worried about changes that could limit the law's Medicaid expansion, which, according to Gov. Christie, has helped cover 487,000 previously uninsured New Jerseyans, with federal funding that has saved the state $2 billion.

"I need to understand what the impact is going to be in New Jersey, if this gets frozen or cut off in the next couple of years," MacArthur said. Christie "gave me pretty dire predictions about what happens."

Others declined interview requests or issued statements that placed them firmly on the fence.

"The congressman is reading the entire text of the bill that was presented last night -- as should be expected of any lawmaker on an issue as important as health care," said a spokesman for Rep. Brian Fitzpatrick (R., Pa.) of Bucks County.

Local Effects of the Two Health Plans

Both the Affordable Care Act and an alternative proposed this week by House Republicans use tax credits to subsidize premiums for health insurance bought on the individual market. But the GOP plan would give lower-income households comparatively less help than they get under the ACA.
Families with lower incomes that receive Medicaid could face a separate challenge, as the GOP plan calls for reducing the federal contribution to the program.
Here is how health insurance tax credits* would play out in the Philadelphia region in 2020, according to the Kaiser Family Foundation:

*Tax credits under the ACA (but not GOP) are higher in Southeastern Pennsylvania because insurance costs more there. These comparisons do not include additional cost-sharing assistance averaging more than $1,000 for lower-income households buying certain plans that is provided by the ACA but not by the GOP’s American Health Care Act.
SOURCE: Kaiser Family Foundation
Staff Graphic

Rep. Charlie Dent (R., Pa.) of Allentown said in a statement that he was "continuing to thoroughly review and evaluate" the plan, "paying special attention to its impact on Pennsylvanians."

One of the region's most conservative voices, Rep. Scott Perry (R., Pa.), joined those on the right skeptical of the proposal.

"While I support the repeal, I'm still concerned about the alternative," he said in a statement. "I agree with President Trump that this is a starting point for negotiation."

They might not have much time; two key House committees are set to debate the bill Wednesday, though they still lack a Congressional Budget Office analysis predicting how much it would cost or how many people might lose health coverage.

Republicans have voted dozens of times to repeal the law and used criticism of the Affordable Care Act and its mandates to help propel them to power in Congress and statehouses across the country.

Now that they control Congress and the White House, their ideas carry far more weight.

The caution Tuesday reflected the complexities of overhauling the health care system, as President Barack Obama did, and the fractious politics surrounding one of the GOP's signature promises.

"It's very easy to be against Obamacare or for Obamacare, but lots of people really benefitted from that, and Republicans, and especially moderate Republicans, are going to want to make sure that anything that replaces it makes sense for their constituents," said Stuart Shapiro, a former Philadelphia health commissioner, now a private consultant. "They don't want to be tagged with something that clearly at this point is unclear."

The issue already is roiling voters and powerful interest groups.

Energized constituents on the left have flooded Republican offices demanding that the law be left in place and sharing stories about its benefits. Protesters touted the law outside Toomey's office Tuesday.

Four Senate Republicans from swing states, meanwhile, warned that they might not support the House bill for fear of how it would affect Medicaid expansions in their states, echoing concerns raised by officials in Pennsylvania and New Jersey. On the right, three Republican senators and an array of powerful conservative groups -- including the Heritage Foundation, the Club for Growth, and Americans for Prosperity -- spoke out against the bill, arguing that it would not go far enough in wiping Obama's law off the books.

"Republicans in the House promised to fully repeal the law -- all the mandates, all the taxes, everything. This proposal from last night does not do that. It simply does not get the job done," said Tim Phillips, president of Americans for Prosperity.

His group, including chapters in Pennsylvania and New Jersey, is planning to bombard Republicans with demands to erase the law. They handed out signs to activists reading "You Promised," and highlighted stories of people who said that their premiums spiked or that they could not see the doctors they prefer since the law was passed in 2010.

With Democrats firmly opposed to any rollback, it would take just three GOP defections to block the measure.

At stake is a law that has helped millions gain access to health insurance, but that critics say has led to higher prices, growing deductibles, and too much government interference in health-care decisions.

With Trump in office, Republicans have a repeal within reach, but the law may be gaining steam with the public. A Pew poll last month found that 54 percent of Americans supported it, its best rating ever.

In Pennsylvania, Wolf administration officials said the state's uninsured rate has fallen to the lowest levels in history, and they credited the law with helping more than 700,000 enroll in Medicaid, part of 1.1 million they said have gained health insurance because its provisions. They feared that the proposed changes could limit new people from enrolling in Medicaid in the future.

Democrats warned that people who have gained coverage could lose it, and they took firmer stands on the latest proposal.

"This repeal bill would force millions of Americans to pay more money for worse health insurance that's attainable for fewer people," said a release from Sen. Cory Booker (D., N.J.).

Sen. Bob Casey (D., Pa.) took to the Senate floor to call it "a scheme, not a plan."

Republicans still have to decide if it is worth backing.

Staff writers Maddie Hanna and Andrew Seidman contributed to this article.