It isn't really the Democrats they need to worry about. What do the independents think?
I have not seen anything about independents yet. That poll did include D-leaning independents.
Sanders continues to prompt some of the same divisions he did in 2016, garnering lower support among self-identified Democrats and older voters. Among those who consider themselves Democrats, 34% back Biden, 11% Harris, 9% Sanders and 8% Warren. Among independents who say they lean to the Democratic Party, however, Sanders stands in second place, with 21% (Biden has 31%, Warren 8% and Harris 7%).
Harris appears to be the biggest beneficiary of Sanders' challenges among Democratic partisans. Among those self-identified Democrats who consider themselves liberal, Harris' support spikes to 19%, still behind Biden at 27% but well ahead of Sanders, who earns just 7% support among that group.
When you add Democratic-leaning independents back to the mix, liberals are more evenly split, with 28% behind Biden, 15% Harris, 13% Sanders and 11% Warren. Among Democrats and Democratic-leaners who consider themselves more moderate or conservative, Biden stands well above the rest: 38% Biden, 14% Sanders and all the rest in single digits.