President-elect Donald Trump and Republicans are wary of the political consequences they may suffer for repealing Obamacare.

Not only have roughly 20 million Americans gained health coverage as a result of the landmark law, but many of those people live in areas of the country that delivered Trump the White House.

Related: Americans with pre-existing conditions could lose coverage if ACA repealed

A new analysis of Gallup polling data by the American Communities Project suggests that counties that voted strongly for Trump have the most to lose from a repeal of the Affordable Care Act.

ACP broke counties into different categories based on their demographics. Of the eight categories of counties that saw health coverage increases larger than the national average over the past eight years, six broke for Trump in the presidential election.

Counties with large Native American populations –– dubbed “Native American lands” –– saw the greatest increase in health coverage as a result of the ACA, rising more than 14 percent since 2008. Trump won such counties by 5 percentage points.

Counties classified as rural working class by the ACP saw the second greatest gains in health coverage during the time period: 6.8 percent. Many of these counties were where Trump did the best, winning on average by a whopping 46 percentage points.

In third place for the greatest increase in coverage (5.8 percent) were “Graying America” counties with disproportionate numbers of senior citizens.

Communities with aging populations are found throughout the country but are particularly common throughout the midwest, where Trump’s strong performance won him several states that had not voted for a Republican presidential candidate in a generation.

In recent weeks, Republicans have suggested that the repeal bill they plan to pass may not go into effect for as many as four years.

They say it will allow them time to craft a replacement that will offer an alternative to those who are currently dependent on ACA coverage, while Democrats say their reluctance to repeal the law is simply evidence that Republicans are facing the fact that the law they have decried for years is actually doing some good.