Thirty-one states and the District of Columbia have expanded eligibility for the government health care program since 2014, using federal money made available by the law to cover poor, working-age adults, a population that was historically not eligible for the coverage.
Resistance to the expansion has remained strong in many red states, including most of the South. And the law remains deeply polarizing with Republicans and Democrats still split on its merits.
But the GOP's effort this year to roll back the law and weaken coverage protections proved even more unpopular. Fewer than 1 in 5 Americans backed the leading Republican repeal bills.
Independent analyses of the GOP repeal bills by the Congressional Budget Office and others estimated they would leave tens of millions more Americans without health coverage and drive up costs for many older and sicker consumers.
That, in turn, has helped shift the health care debate nationally. A Pew Research Center poll over the summer found that 60 percent of Americans believe it is the federal government's responsibility to ensure all Americans have health coverage -- the highest level in nearly a decade.
In Maine, advocates had been working unsuccessfully for years to enact a Medicaid expansion over the fierce opposition of the state's Republican governor, Paul LePage, a vocal supporter of Trump.
LePage and his allies worked hard to defeat the Medicaid measure. But on Tuesday, the results weren't even close. The Medicaid measure passed 59 percent to 41 percent.
"This should be sending a message to the 18 other states that haven't yet expanded Medicaid," Robyn Merrill, executive director of Maine Equal Justice Partners, said a victory speech Tuesday night.
Medicaid wasn't on the ballot in Virginia, but exit polling suggests the issue had similar resonance there.
Six in 10 voters in Virginia said the state should expand the program, according to a survey by Public Policy Polling conducted for Protect Our Care, an advocacy organization formed to fight the GOP effort to repeal the Affordable Care Act.