Reason?
Probably more people running and Elizabeth Warren in particular…
Pew Research Center has been interviewing a consistent panel of voters since the 2016 nominating contest. That allows them to compare views of the current field with the preferences of the same voters four years ago.
Those who supported Hillary Clinton four years ago are most likely to now support Biden, rather unsurprisingly. So is the group of voters who at different times during the 2016 campaign indicated they supported either Clinton or Sen. Bernie Sanders (I-Vt.), or who had no opinion. About 17 percent of that group now supports Sanders.
Interestingly, while Sanders is the most commonly supported candidate among his 2016 backers, a quarter of his support from four years ago now goes to Sen. Elizabeth Warren (D-Mass.). Warren also scoops up a bit over a tenth of Clinton’s 2016 support.
A Twitter user wondered why Sanders was nonetheless in the top tier of the field. RealClearPolitics’s average of polls has Sanders in second place, with support of 22.5 percent of the electorate. But that’s far less than the support he had four years ago at this point, when he was supported by more than 37 percent of the electorate. Back then, there were only two significant candidates. Now, there are more — and Sanders’s strong core base of support keeps him in the hunt even though his support is lower than it was.