Despite years of Republican efforts in Washington to repeal the Affordable Care Act, support in Virginia for Medicaid expansion remains as strong as ever.

A new University of Mary Washington survey of 1,000 adult Virginians found that 70 percent favor increasing access to Medicaid, an important but optional part of the Affordable Care Act, with only 25 percent opposed. A year ago, 68 percent said they wanted Virginia to expand this public health-insurance program for low-income, uninsured state residents.

Gov. Terry McAuliffe (D) favors Medicaid expansion, but Republican majorities in the legislature do not. Despite a federal reimbursement program for states that expand Medicaid that will cover nearly all the added expenses, GOP lawmakers predict Virginia taxpayers eventually will be stuck with much higher costs.

Medicaid enrollment is greatest in the commonwealth's most urban and the most rural areas. Nearly every House of Delegates district south of Interstate 64 and west of Interstate 95 has Medicaid enrollment levels above the state average, as do districts in Richmond and Hampton Roads. These areas are most likely to benefit from Medicaid expansion.

In the September UMW survey, 50 percent of Republicans favor the idea, with 44 percent opposed. In contrast, 92 percent of the state's Democrats and 66 percent of independents favor covering more people under Medicaid.

Few policy issues generate such strong public support, but the measure languishes in Richmond because of gerrymandering, not citizen preferences.

When lines are drawn to create legislative districts favoring one party to an overwhelming degree, politicians of that party are far more at risk of losing in a party primary than in a general election. In 2015, only 29 of the state's 100 delegate elections featured Democratic and Republican candidates. Only six were close contests, decided by fewer than 10 points.

In such a political environment, Republican lawmakers rightly fear angry conservatives far more than any other voting group. Any safe-seat Republican who sides with McAuliffe on Medicaid expansion — even if he or she represents a district that would benefit — would likely be defeated in a low-turnout primary by a more conservative opponent.

Given hyper-partisan line-drawing, the 70 percent public support shown for this policy change does not mean much. Medicaid expansion remains a long way from being enacted in Virginia.

The writer is a professor of political science at the University of Mary Washington and director of the university's Center for Leadership and Media Studies.