Andy Thorburn, a health insurance executive who is plugging $2 million into a bid to replace Rep. Edward R. Royce (R-Calif.), is the latest Democrat pushing the party to embrace single-payer health care — even in swing districts. In a video announcement, Thorburn paints the contest as a referendum on health care, between a Republican who voted for the repeal of the Affordable Care Act and a Democrat who wants to move, eventually, to “Medicare for all.”

. . .