These charts reflect the results of the Quinnipiac University Poll -- the latest of which was done between October 4th and 7th of a national sample of 646 Democratic and Independent (leaning Democratic) voters, with a 4.7 point margin of error.
The top chart reflects the current standing -- with Warren having 29%. That's 3 points more than Biden and 13 points better than Sanders.
The bottom chart shows how these three have done in Quinnipiac polls since April.
Sanders has gained slightly -- going from 11% in April to 16% in October.
Biden has dropped some support -- from 38% in April to 26% in October.
Warren has shown a steady gain in support -- from 12% in April to 29% in October.