From CNN: Overall, 27% of registered voters who are Democrats or Democratic-leaning independents back Sanders, while 24% favor Biden. The margin between the two is within the poll's margin of sampling error, meaning there is no clear leader in this poll. Both, however, are significantly ahead of the rest of the field, including Massachusetts Sen. Elizabeth Warren at 14% and former South Bend, Indiana, Mayor Pete Buttigieg at 11%. Former New York Mayor Michael Bloomberg lands at 5% in the po