The chart above reflects the results of the latest Quinnipiac University Poll -- done between January 22nd and 27th of a national sample of 827 Democratic primary voters, with a 3.4 point margin of error.
The chart above reflects the results of the latest Economist / YouGov Poll -- done between January 26th and 28th of a national sample of 591 Democratic primary voters. (No margin of error was given for just this sample.)
The chart above reflects the results of a new Pew Research Center survey -- done between January 6th and 19th of a national sample of 7,013 Democrats and Leaners, with a 1.8 point margin of error.