Here's your guide to how key parts of the ACA might be impacted by Republicans' push for repeal. Major provisions and public opinion ratings (percent Americans who say they have a favorable opinion of each provision) are from the Kaiser Family Foundation’s health tracking poll from November 2016.

Republicans in Congress have not yet put forward a replacement healthcare plan, but the president-elect has promised his party would repeal and replace the ACA " essentially simultaneously ".

President-elect Donald Trump has said he would consider keeping some of the more popular pieces of the law in place, including a provision that lets young adults stay on their parents’ health insurance until age 26 and another that prohibits insurers from denying coverage to people with pre-existing medical conditions. But these provisions rely on other, less popular parts of the ACA that Republicans have pledged to cut.

Senate Republicans don’t have the 60 votes needed to outright repeal the ACA. But in January , they set in motion a budgetary process that would dismantle key provisions of the law. The maneuver, known as a budget reconciliation , requires only 51 votes to pass.

Republicans are gearing up to make good on a longstanding promise: to repeal the Affordable Care Act – or Obamacare, as it’s commonly known.

Public favorability 35% Individual mandate Requires Americans to have health insurance How it works now: This provision requires citizens and legal residents to have health insurance coverage or pay a tax penalty. The individual mandate is unpopular – but it makes many other parts of the ACA possible. To cover sick people without charging exorbitant prices, insurers need to balance enrollment with young, healthy people too. But those people might not get health insurance if they weren’t required to. How it could go: Republicans need a Senate supermajority (60 votes) to repeal this requirement outright – an unlikely scenario. But they can eliminate the tax penalty associated with the mandate through a simple majority (51 votes) using budget reconciliation. Americans would still be required to purchase insurance, but there would be no consequences if they did not.

Public favorability 60% Employer mandate Requires medium and large businesses to offer health insurance coverage for employees How it works now: This provision requires businesses with more than 50 employees to provide affordable health insurance or pay a penalty determined through a complex formula. How it could go: Republicans could repeal the penalty businesses pay, while leaving the requirement to provide health insurance through a simple majority vote. This would give businesses little incentive to comply with the mandate, leaving many workers uninsured – especially if subsidies for non-employer plans are eliminated.

Public favorability 69% Medicare payroll tax Increases rate for upper-income Americans How it works now: Individuals who earn more than $200,000 a year and married couples that earn more than $250,000 a year pay an additional 0.9% payroll tax, which helps to finance preventive services and provides prescription plan discounts for the elderly and additional resources to doctors. This tax extended the solvency of the Medicare trust fund by 12 years. How it could go: Republicans could eliminate the Medicare payroll tax through a special budget maneuver. Eliminating the tax would cost the government $123bn in revenue over nine years.

Public favorability 69% Pre-existing conditions Prohibits insurers from rejecting people with prior diagnoses How it works now: The ACA bans insurance companies from declining to cover patients with previous medical diagnoses. In the past, even minor health blemishes could result in a rejection from the insurance market. How it could go: Republicans, including President-elect Donald Trump, have embraced this popular provision. But the measure is financed through another less popular element of the ACA: the individual mandate. In order to cover sick and high-risk people at an affordable price, insurers need young, healthy people to sign up to balance out costs. But these people have less incentive to get health insurance without a mandate. Republicans have proposed Republicans, including President-elect Donald Trump, have embraced this popular provision. But the measure is financed through another less popular element of the ACA: the individual mandate. In order to cover sick and high-risk people at an affordable price, insurers need young, healthy people to sign up to balance out costs. But these people have less incentive to get health insurance without a mandate. Republicans have proposed high-risk pools as an alternative to guarantee coverage. High-risk pools existed for decades before the ACA. They helped extend insurance to people with pre-existing conditions, but at high costs.

Public favorability 80% Insurance exchanges Creates marketplaces for individuals and small businesses to buy coverage How it works now: Probably the best known provision of the ACA, exchanges allow individuals and small businesses to compare and purchase health insurance online – the same way you would compare hotel rates or plane tickets. Previously, people who did not get insurance through their employer but wanted a plan had to call insurers directly. How it could go: It would be hard to get rid of exchanges outright, but Republicans could eliminate the subsidies that make exchange plans affordable for most Americans with a simple majority vote. That would effectively kill exchanges by making the health insurance they offer unaffordable. The subsidies represent most of the federal cost of the program (more on subsidies below).

Public favorability 80% Health plan subsidies Provides financial aid to low- and moderate-income Americans to buy coverage How it works now: Individuals who don’t get insurance from their jobs can buy insurance through exchanges. The government provides subsidies to people with incomes between 100% and 400% of the federal poverty level (an income of $11,880 to $47,520 a year for individuals, or $24,300 to $97,200 a year for a family of four). How it could go: Republicans could eliminate these subsidies with a simple majority vote. 9.3 million Americans currently receive health plan subsidies, which average around $300 per month per household. Previous Republican repeal proposals have offered less generous subsidies or limited them to high-risk populations.

Public favorability 80% Medicaid expansion Provides coverage to more low-income adults How it works now: The ACA expanded Medicaid to cover low-income adults earning up to 138% of the federal poverty limit ($27,821 for a family of three in 2016). To help states finance the expansion, the federal government picks up at least 90% of the tab. In June 2012, the US supreme court ruled that Medicaid expansion should be optional for states. To date, 19 states have not expanded Medicaid. In those states, a family of three must earn 44% or less of the poverty limit to enroll ($8,870 for a family of three), while low-income, childless adults are mostly ineligible for the benefit. How it could go: Republicans fought this provision tooth and nail, bringing it all the way to the highest court. Nevertheless, many Republican governors found it practical to expand Medicaid to provide care for millions of residents. An estimated 11 million adults received health insurance through the expansion. Republicans want to end federal subsidies – and can do so with a simple majority vote.

Public favorability 81% Doughnut hole&39; rule Closes the prescription coverage gap for Medicare patients How it works now: Before the ACA, Medicare didn't cover the costs of all prescription medicines – a gap known as the "doughnut hole". The health law provides additional benefits to seniors and is designed to close the gap by 2020. How it could go: Republicans could end this subsidy to seniors and reopen the “donut hole” through the budget reconciliation process. Millions of seniors would then need to pay more for prescriptions.

Public favorability 83% Free preventive services Prohibits out-of-pocket costs for checkups How it works now: Preventive health screenings are covered for free. This includes routine tests such as cholesterol screenings, vaccines for children and women's health services. How it could go: Republicans would have difficulty repealing this provision on their own; they would likely need Democrats to join in a supermajority vote – which is unlikely. But Republicans may not see a reason to scrap this popular part of the ACA anyway. Insurers may have a hard time paying for these services without the additional customers the ACA delivers through the individual mandate.

Public favorability 85% Coverage for young adults Allows adult children to stay on parents’ health plans How it works now: The ACA requires that insurers cover young adults as part of their parents’ health insurance plan through age 26. Previously, the cut-off age varied by state and by plan. How it could go: President-elect Trump appears keen on keeping this provision, but Republicans have little power to cut it either way. The provision can’t be scuttled with a budget reconciliation, because it doesn't rely on federal funding.

Public favorability N/A Ban on coverage limits Prohibits annual and lifetime spending caps on most healthcare benefits How it works now: Insurance companies are banned from placing a dollar amount on lifetime or annual coverage. The practice was common before the ACA, and tended to affect patients with complex or chronic illnesses, such as cancer or diabetes. How it could go: Republicans are likely to keep this provision but if the individual mandate disappears, it's unclear how insurers would finance it.

Illustration by Jan Diehm.