An Emerson national poll released Tuesday showed Bernie Sanders winning a head-to-head matchup, too.
Biden would defeat Trump 54% to 46%, and Sanders leads the president 52% to 48% in the survey conducted this week. Both results are within the margin of error of 2.5%.
Elizabeth Warren and Kamala Harris both tied against Trump. Pete Buttigieg trailed by 2 percentage points.
In the Democratic primary contest, Emerson found Biden leading 31%, followed by Sanders with 24%, Warren with 15% and Harris with 10%. No other candidate had more than 4%.
Buttigieg, whose standing has eroded over the summer, was in fifth place among Democrats at 3%, behind Andrew Yang, who had 4%.
A Monmouth University poll on Monday showed a virtual three-way tie among Sanders, Warren and Biden.
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