(Bloomberg) --Republican lawmakers will overturn a key piece of the Affordable Care Act in their tax overhaul, a victory in a long GOP campaign against the health law.

Senate Majority Leader Mitch McConnell said the compromise tax bill from House and Senate negotiators will end the health law’s requirement that all individuals buy insurance or pay a fine. Doing so could jeopardize Obamacare’s already-shaky marketplaces, by reducing the number of healthier people who sign up for insurance.

The bill will “repeal Obamacare’s individual mandate tax, delivering relief to low- and middle-income Americans who have struggled under an unpopular and unworkable law,” the Kentucky Republican said in an emailed statement.

Senate majority leader Mitchell McConnell
Senate majority leader Mitchell McConnell

The new tax legislation must still be approved by both houses of Congress. Republicans hold a narrow 52-48 majority in the Senate, which will be further diminished when Alabama Democrat Doug Jones takes his seat.

The bill will also include a two-year tax break for individuals with high medical expenses, according to two senior congressional aides who described the provision on condition of anonymity. The provision lowers the amount people have to spend on health costs before they can deduct those costs, to 7.5 percent of their income, from 10 percent under current law.

The House had proposed eliminating the medical costs deduction, as a way of raising revenue for other tax cuts. Its expansion was pushed for by Senator Susan Collins, the Maine Republican whose vote is crucial to passing the tax package.

Undoing Obamacare’s mandate was one of a handful of specific changes McConnell mentioned in his statement. He also said the bill would lead to “further developing Alaska’s oil and gas potential,” a likely reference to opening the Arctic National Wildlife Refuge to drilling.

Opening the refuge to the energy industry is an attempt to ensure the compromise bill has enough votes to pass. Alaska Republican Senator Lisa Murkowski has previously opposed efforts to repeal the Affordable Care Act but she’s long pushed for Arctic drilling.

Updated December 13, 2017 at 5:16PM: Updated version

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