The Chart above is the latest Economist / YouGov Poll -- done between September 8th and 10th of a national sample of 632 Democrats and Leaners (no margin of error given). This weekly poll has Elizabeth Warren equal to Joe Biden (both at 24% support).
Other polls show Biden still leading, but all have shown Warren is climbing. She is winning over more Democrats with each passing week.
The chart below seems to verify Warren's rise. It is the latest NPR / PBS NewsHour / Marist Poll -- done between September 5th and 8th of a national sample of 542 Democrats and Leaners. The margin of error is 5.6 points.
It shows Warren with the highest favorable rating (75%), and tied with Buttigieg for the lowest unfavorable rating (11%) of any of the leading Democratic candidates.