This is the poll that has Donald Trump shaken. It shows. the four leading Democratic candidates would all beat Trump if the election was held right now -- Biden by 12 points, Sanders by 9 points, Warren by 7 points, and Harris by 6 points. All of those advantages exceed the poll's margin of error.
The charts on this page are from the new Fox News Poll -- done between August 11th and 13th of a national sample of 1,013 registered voters, with a margin of error of 3 points.
The poll also questioned 483 Democratic primary voters about their preference for the Democratic presidential nomination. The margin of error for them was 4.5 points.
The results of the Democratic preferences are below. It shows that only one of the leading Democratic candidates has increased support since March -- Elizabeth Warren by 16 points (going from 4% to 20%). She has now moved into second place.
Joe Biden (31%) and Kamala Harris (8%) have the same support they had in March. The big loser is Bernie Sanders, who is down 13 points (from 23% to 10%).