Congressional districts that tend to vote Democratic generally have more people below the poverty level and higher uninsured rates compared to those that tend to vote Republican, including districts in states that have expanded Medicaid.
Between the lines: There's an obvious connection between poverty levels and the number of uninsured: Health insurance is expensive. The fact that blue districts have higher shares of each than red districts helps explain why Democrats tend to focus more than Republicans on health care and government assistance to the poor — and why these topics will likely resonate with voters in blue districts more throughout the midterm cycle.