Warren and Sanders backers have some clear ideological similarities in the post-debate poll — 89% of Sanders backers have a favorable view of democratic socialism (Sanders identifies as a democratic socialist), as do 80% of Warren backers. Biden voters were much more split: 35% had a favorable view, 30% unfavorable, and 34% were unsure. A quarter of Sanders supporters said they considered themselves to be democratic socialists, compared to just 12% of Warren supporters.



In total, 75% of Warren backers and 71% of Sanders backers considered themselves progressive, liberal, or democratic socialist. That was true of only 42% of Biden backers, 43% of whom identified as politically moderate.

Another way of looking at ideological sorting in the poll: how voters with different health care preferences are lining up behind candidates. Seventy-five percent of those who back Sanders, who has made Medicare for All central to his campaign, support a single-payer health care system, and 16% support a public option, where Americans would be able to choose between a government plan and private insurance. Those numbers are virtually flipped for Biden supporters: 79% back a public option and 16% back single payer. Warren supporters were nearly evenly split between a public option and single-payer, 44%–50%.

The pre-debate survey had a sample size of 1,784 likely Democratic primary and caucus voters, and the post-debate survey had a reinterview rate of 72%, for a sample size of 1,291. The poll, which was conducted online, has a margin of error of 3.1%.