A Washington Free Beacon analysis of census data and early primary results found that Sanders finished no higher than third and as low as fifth in the three Iowa counties with the highest proportion of privately insured adults. In New Hampshire’s Rockingham County, where 83 percent of adults have private insurance, Sanders lost by 4 points to former South Bend, Ind., mayor Pete Buttigieg and nearly dropped to third behind Sen. Amy Klobuchar (D., Minn.).

Sanders has campaigned on a Medicare for All proposal that would end private health insurance. His failure to succeed in areas with high concentrations of privately insured voters reinforces concerns that the Vermont senator could undermine down-ballot Democrats in the general election. Suburban districts key to the House majority also hold high proportions of privately insured adults. Democratic candidates across the country are retreating from Medicare for All even as Sanders emerges as the frontrunner in a crowded primary field.