It wasn’t easy, but Republican leaders in the House finally wrote and then released on Monday a bill to accomplish the party’s long-held goal of repealing and replacing the Affordable Care Act. The Trump administration is fully behind the repeal effort. And the Republicans have the votes, assuming everyone falls in line: They need 50 of the 52 Republicans in the Senate and 216 of 237 Republicans in the House to get the legislation adopted.

But this legislative debate is far from over. Health care, as the president recently said, is a very complicated issue, with potentially deep ramifications from even the smallest change. Obamacare was a sweeping, comprehensive bill. And Republicans, by putting out a fairly comprehensive bill, tried to unwind much of it in one swing.

Health care policy is always about tradeoffs, and the replacement bill that the House Republicans rolled out Monday is likely to rankle several constituencies, who could rev up opposition and mount a fight.

Older Americans

The bill allows health insurers to charge an older person up to five times as much as someone who is younger for the same coverage, compared to the 3-to-1 ratio allowed under the Affordable Care Act. The AARP is already organizing its members to oppose the legislation for this reason.

Conservative lawmakers

Conservative members of the Senate and House, particularly the House Freedom Caucus, complained that early versions of the Obamacare repeal were too modest in rolling back the ACA. Specifically, they said that the expansion of Medicaid under the ACA needed to be ended immediately and that Congress should not create any kind of federal guarantee for health care. But this legislation keeps in place the funding for Medicaid expansion through 2019 and gives most Americans a tax credit to buy health insurance.

Only hours after the bill’s text was made public on Monday, members of the Freedom Caucus were criticizing the legislation and suggesting that they would not vote for it.

Governors

While the Freedom Caucus sees the proposed bill as too generous with Medicaid, governors may see it as too stingy. Under Obamacare, the federal government was scheduled to pay for 90 percent of the costs of new Medicaid expansion enrollees in states. Thirty-one states, including many with Republican governors, had opted to expand their Medicaid programs through Obamacare. Under the House bill, with the federal government no longer committing to fund new recipients of expanded Medicaid, state governments would be left footing more of the bill to offer health care for low-income people.

For Medicaid recipients, the bill essentially says that those on Medicaid through the expansion under the ACA at the end of 2019 can stay on the program with federal funds. But people trying to enroll in 2020 and beyond might be out of luck, since many states don’t feel they can afford more Medicaid recipients without additional federal funding.

The bill also would change how the federal government funds Medicaid; instead of paying for a percentage of states’ programs, it would cap how much the government would pay per Medicaid enrollee.

People currently getting ACA coverage, particularly those with low incomes

Under Obamacare, health care subsidies are tied to income, which means that poorer people generally get more help. In contrast, the House bill would create a universal tax credit. People under 30, for example, would get $2,000 for insurance, whether they make $12,000 or $60,000 a year. (The credits start to phase out for people with incomes above $75,000.)

Americans who get less financial support to purchase insurance under this new system than under the ACA could decide to mobilize against the House bill.

Senate Republicans

Since Election Day, at least 15 Republicans in the Senate have expressed reservations about either the party’s process in repealing Obamacare or the details of the policy.

Five senators (Bill Cassidy of Louisiana, Susan Collins of Maine, Bob Corker of Tennessee, Lisa Murkowski of Alaska and Rob Portman of Ohio) unsuccessfully pushed for a bill that would delay Congress’s start on the Obamacare repeal process. (Saying that something is being rushed or calling for its delay is a common tactic that members of Congress use to oppose things.) Sens. Lindsey Graham of South Carolina, Johnny Isakson of Georgia and Shelley Moore Capito of West Virginia, along with Cassidy and Collins, have proposed allowing states to keep their Obamacare programs as they are now if they choose, including retaining the Medicaid expansion, with no expiration date. Nevada’s Dean Heller and Colorado’s Cory Gardner have also raised concerns about shifting how Medicaid is funded.

Texas Sen. Ted Cruz, Utah Sen. Mike Lee and Kentucky Sen. Rand Paul, like the House Freedom Caucus, have been criticizing the repeal proposals aired by party leaders as “Obamacare lite” and insufficiently conservative, while Tennessee Sen. Lamar Alexander and Arizona’s Jeff Flake have warned Republicans against moving too quickly and overreaching.

Voters, particularly Democrats, who don’t want to see major changes to the law

Surveys by NBC News and The Wall Street Journal, the Kaiser Family Foundation and Pew Research Center have shown that public support for Obamacare has inched up since Election Day. According to Kaiser, 48 percent of Americans now have a favorable view of the law; Pew says that 54 percent of people approve of Obamacare. The Pew number was the highest rating the law has ever received in that poll. In the NBC/WSJ survey, 43 percent of Americans said the law was a “good idea,” compared with 41 percent who disagreed. In contrast, many NBC/WSJ surveys over the last six years had shown that a plurality felt the law was a “bad idea.”

Polling suggests that the Medicaid expansion is very popular, much more so than Obamacare overall. A recent survey by the Kaiser Family Foundation found that 65 percent of Americans favor keeping Medicaid as it currently exists, including 39 percent of Republicans.

And a grass-roots movement has emerged to defend Obamacare. Members of Congress in conservative-leaning states, including Arkansas, Kentucky and Utah, have encountered protesters who are demanding that they leave the law in place.

Do these protests matter? The pro-ACA mobilization is being likened to the anti-Obamacare movement led by conservative tea party activists in 2009 and 2010. Those protests drew lots of public attention, but Democrats still pushed through the ACA.

Politicians generally try to take steps in the direction of public opinion, not against it. That said, according to Pew, the rise in Obamacare support is coming largely from Democrats and Democratic-leaning independents who say they now view the law favorably. The vast majority of Republicans still oppose the law and want it either repealed or drastically changed. Just 22 percent of Republican-leaning independents approve of Obamacare, according to Pew, and just 10 percent of Republicans do.

People who support abortion rights or Planned Parenthood

The bill, as expected, bars Planned Parenthood from receiving reimbursements for services through Medicaid. (Federal law already bans the use of federal funds for abortions.) Murkowski, the Republican senator from Alaska, has long said that she is wary of backing a bill that limits Planned Parenthood funding.

However, all these groups’ concerns about the proposed ACA replacement don’t give Democrats the advantage in the Obamacare fight. The overall dynamics still favor the GOP. The vast majority of the Republican electorate opposes Obamacare, and Republicans have majorities in both houses of Congress. And the repeal effort will have some strong supporters: Trump and his administration, conservative activists’ groups who have long demanded the end of Obamacare, and the leaders of the House and Senate, who say this is a core party goal.

The underlying dynamics of Obamacare repeal are now clear. House Speaker Paul Ryan and his leadership team appear to have tried to put together a bill that unwinds most of Obamacare but does so gradually, leaving some of its Medicaid expansion in place through 2019 and trying to replace its tax credits with a different system of credits that have a similar goal of helping people pay for coverage. The bill seems like an effort to get enough votes from moderates in the Senate and conservatives in the House to pass without completely satisfying either bloc.