By backing the wholesale repeal of the 2010 health care law, President Donald Trump could unravel his own plan on prescription drug prices and undermine his messaging on an important issue ahead of the 2020 election: the climbing cost of medicines.

Less than two weeks before the midterm elections last year, Trump delivered a proposal to rein in the costs of outpatient drugs by pegging them to the lower prices paid by foreign countries.

The policy was endorsed by advocates for lower drug prices and denounced by the powerful lobby for drugmakers, appearing to fulfill a promise Trump made in a speech in the Rose Garden earlier that year to take on the Big Pharma “gravy train.”

Kaiser Family Foundation polling this month found majorities in both parties support the move.

One little-noticed aspect of the proposal, dubbed the International Pricing Index Model is that officials have begun implementing the plan by drawing on the authority granted by the Centers for Medicare and Medicaid Innovation Center. The CMMI is a vehicle for testing new payment models to lower health costs and was established by the 2010 health.

So by doing away with the law — as Trump endorsed Monday by directing the Justice Department to affirm the ruling of a conservative judge that the entirety of the law is unconstitutional — the White House could unravel its own drug pricing proposal.

“The Center for Medicare and Medicaid Innovation has pushed a number of payment reforms and is at the center of any approach to test new approaches to paying for drugs,” said Nicholas Bagley, an expert in health law at the University of Michigan. “Losing it would circumscribe the administration’s ability to tackle the problem.”

Some health care advocates say they would be disappointed if the proposal were nullified.

“As an organization, our focus remains on drug prices set by manufacturers and solutions for Congress, states and the administration to lower prices. The [International Pricing Index Model] is certainly one of those solutions and we’d be disappointed to see it come off the table,” said David Mitchell, the president of Patients for Affordable Drugs, an advocacy group whose campaign arm mounted a $1 million ad campaign in support of the policy.

The reversal could also open Trump up to criticism that he has failed to act on a priority that polls show a wide swath of voters care about.

“Drug prices will be a top issue in 2020,” Mitchell said.

Two top polling candidates in the Democratic primary, Sens. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, have both put forward sweeping changes to the pharmaceutical industry.

“If the Supreme Court rules that Obamacare is out, we’ll have a plan that is far better than Obamacare,” Trump told reporters this week. But such a plan is not in the works, congressional Republicans said.

Neither the White House nor the Centers for Medicare and Medicaid Services, which oversees the Innovation Center, replied to questions submitted to them last week.

Watch: Wyden: Drugmaker protects Humira exclusivity ‘like Gollum with his ring’

An ad campaign by the American Conservative Union has already touted the president’s actions on drug pricing to “end foreign free-loading,” including a Twitter video that has accrued nearly 2 million views. (The conservative group opposes the International Pricing Index Model, but backs the president’s actions to strengthen patent protections abroad, an action with unclear benefits at home.)

And if the midterms are any guide, Republicans will tout drug pricing plans to deflect from criticism that they have not put forward counterproposals on health care to rival the health care law or “Medicare for All.”

Last year’s unveiling of the White House proposal on drug prices came as congressional Republicans on the campaign trail faced an onslaught of criticism for their health care votes.

Democrats hit Republicans in competitive districts for voting to repeal the ACA without replacement legislation that retained its protections for people with pre-existing health conditions; Republican leaders in Congress have privately acknowledged that their positions on health care may have cost the party control of the House.

During the election, Republican National Committee spokeswoman Kayleigh McEnany defended Republican votes on health care on Fox Business in part by citing the International Pricing Index Model.

McEnany said Trump “is taking care of our seniors, taking care of American consumers, and bringing down drug costs.”