House Republican leaders struggling to pass their alternative to the Affordable Care Act are colliding head-on with the GOP’s new demographic reality: Their coalition is centered on older white voters, many of whom fear losing benefits from the Obama-era law.

An Atlantic analysis shows that House Republicans who have expressed opposition to the GOP’s replacement plan are heavily concentrated in districts where the median age, the number of seniors, or both exceed the national average. Because President Trump ran so well in older and often blue-dollar districts, that dynamic produces a paradoxical result: Most of the House Republicans expressing hesitation about the bill, whose passage Trump supports, represent districts he carried. In most of those seats, Trump improved on the performance of 2012 GOP nominee Mitt Romney.

That unexpected pattern underscores the GOP’s continuing difficulty reconciling its traditional small-government ideology with the material needs of the older and lower-income whites increasingly central to its coalition. While retaining the traditional conservative skepticism of programs targeted at the poor, those older whites have departed from conservative dogma by consistently expressing support in polling for government programs—from Medicare to Social Security—that they believe would benefit their own families. As the House’s legislative struggle suggests, it appears the ACA may be joining that list.