Viewers of the latest Democratic primary debate were most impressed by Bernie Sanders, Joe Biden and Elizabeth Warren, but they also said the debate left them feeling more nervous than optimistic about the candidates, according to a poll released Wednesday.

The survey from CBS News, which hosted Tuesday's debate in Charleston, South Carolina, found that 26% of viewers thought Sanders made the best case that he could beat President Donald Trump in the 2020 election.

Biden followed, with 21% saying the former vice president made the best case, and 12% chose Warren, the senator from Massachusetts. Former New York City Mayor Mike Bloomberg finished fourth at 11%, despite Warren's description of him during the debate as the riskiest candidate in the group.

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Sanders – the current Democratic front-runner after winning the Nevada caucuses and New Hampshire primary – was also viewed as the most impressive candidate overall by debate viewers, at 45%. He was followed closely by Biden at 43%, Warren at 40% and former South Bend, Indiana, Mayor Pete Buttigieg at 38%.

A majority of respondents also thought the senator from Vernont, the most frequent target of attacks during the contest, did a "good job" of explaining his views on communist governments. Sanders said in a "60 Minutes" interview on Sunday that it was "unfair to say everything's bad" about Cuba's communist government under Fidel Castro, pointing to his literacy program. Forty-three percent thought he did a "bad job" of explaining the remarks.

The likely voters polled did have overall criticisms of the debate, with 47% saying it made them feel nervous about the group of candidates. But optimistic viewers were not far behind at 42%, and 25% said they felt inspired after the debate.

The decorum of the candidates during the debate also seemed to irk some viewers. A large majority – 69% of those polled – said the candidates spent more time criticizing each other than making a case for themselves on Tuesday night. However, 52% also said the debate made the candidates' ideas and platforms more clear.