Obamacare’s days may be numbered. The Affordable Care Act has survived dozens of recall attempts by the House of Representatives and two challenges brought to the U.S. Supreme Court.  But with a Donald Trump presidency and a new Republican-led House and Senate, the bill—or at least certain key provisions—is almost certainly headed for the chopping block.

The question now is what provisions may survive and when the death knell of the others will sound.

President-elect Trump campaigned on repealing the law and its requirement for Americans to carry health insurance. Trump says the private market should step in with the sale of insurance plans across state lines to help drive down costs through competition. He has said he will dismantle Medicaid and transform it into a system of state grants to provide assistance for low-income residents.

Until now the twin shields of Pres. Barack Obama’s veto power and the threat of filibuster—a Senate procedural tool that allows senators to slow or stall legislation—have helped prevent Republicans from repealing Obamacare. Overcoming a filibuster requires a vote from 60 senators.  Even with the new Republican-led Senate, lawmakers will not have those 60 votes—but House Speaker Paul Ryan has already sketched out a blueprint for sidestepping those obstacles in the next Congress by employing a budgetary process called reconciliation. This approach is not subject to filibuster in the Senate and limits the addition of amendments. With this maneuver only 51 senators would need to approve an action once it clears the House. The process, created in 1974, is designed to speed up certain tax, spending and debt limit legislation and has been employed a couple dozen times. Under reconciliation restrictions Senate debate on a bill is capped at 20 hours, and debate on any compromise between the two chambers is limited to 10 hours—ensuring relatively swift action.

Republicans have already used this approach to push through a bill aimed at repealing Obamacare, but Obama vetoed it when it came to his desk. President-elect Trump, however, would almost certainly sign such a bill into law. With a Republican-led Congress, a reconciliation bill would go further than the bill that previously made it to the Oval Office, says G. William Hoagland, senior vice president at the Bipartisan Policy Center, a Washington, D.C. think tank. “They would probably replace the subsidy system in Obamacare with tax credits on the purchase of health insurance,” he says. “So they would repeal and replace Obamacare.”

Reconciliation is a limited tool. It could only alter provisions of Obamacare that would officially have a federal budgetary consequence. So regulatory changes imposed on the private sector insurance market—such as altering how state health insurance markets are organized or changing the requirement to cover adults under age 26, if desired—would not be included. But something like a change to Medicaid coverage, or tax requirements related to the Affordable Care Act, would be eligible. (If lawmakers first changed a provision of the law that oversees the reconciliation process to allow matters beyond those that affect the federal budget to be included, then there could be more extensive action, says Jack Hoadley, a  research professor in the Health Policy Institute at  Georgetown University.)

Exactly how many Americans would remain insured following an Obamacare repeal is subject to many moving parts, including individual state actions. “Obviously Medicaid expansion was a piece of the law, and perhaps some states would continue that with state dollars so that would affect how many people gain or lose insurance,” Hoadley says. A state could try to maintain an exchange marketplace on its own, but it would have to come up its own subsidy dollars out of its own state monies, he says.

Repealing Obamacare could not happen overnight, however. Passing a straight overhaul of the act without reconciliation remains unlikely, because the action could get mired by a Senate filibuster. But in order for lawmakers to use a reconciliation bill they would first need to have a budget. Because a budget would not be introduced until February—or perhaps March—and then the House and Senate would have to agree on it, it is unlikely that a bill would get to the president’s desk until around August recess, Hoagland says. “That reconciliation bill could include things other than Obamacare, including tax reform, so once you start putting that kind of bill together you are not talking about doing this in the first 100 days,” he adds. 

The timeline may get even longer if there is no good agreement on an exact formula for replacing Obamacare, Hoadley says, noting that repeal is much less contentious than the formula for its replacement. “We have been operating under this law for five to six years, so repealing and replacing it is a different animal now than it would have been if we had this conversation in 2011, before a lot of the provisions took effect.”