Though the difference is within the margin of error (3.4 percentage points) 39 percent of the 1,108 adults surveyed between December 18 and 19 preferred Sanders over Trump, compared to 37 percent who preferred Biden.
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In the Ipsos/Reuters poll, Sanders is supported by more independents (21 percent) and Democrats (74 percent) than both Biden and Warren in matchups against Trump, but the president nonetheless claims more of the independent vote against Sanders, Biden and Warren.
In another measure of electability, however, the Sanders-Trump comparison compels more people to vote at the end of the day, according to the survey. Only 20 percent of respondents say they wouldn't vote if the election were held between Sanders and Trump. That's compared to 23 percent and 21 percent who said the same of Biden and Warren versus Trump, respectively.