Oct. 25, 2019 — A series of recently released national political polls finds former Vice President Joe Biden re-establishing the type of horse race leads over the Democratic field that he enjoyed before the debate process first began. Yet, how reliable are the polls?
CNN, YouGov, Emerson College, and HarrisX, all report new data and see Biden again posting significant leads, two of which are well beyond the polling margin of error.
CNN (Oct. 17-20; 424 US Democratic registered voters) gives the ex-VP a 34-19-16 percent lead over Sens. Elizabeth Warren (D-MA) and Bernie Sanders (I-VT). HarrisX (Oct. 21-22; 440 US registered Democratic voters) finds the Biden lead reaching 27-19-14 percent over Warren and Sanders. Emerson College (Oct. 18-21; 430 US Democratic likely voters) sees a similarly close cut among the top three candidates, but they find Sen. Sanders slipping past Warren into second place. The Emerson split shows Biden up 27-25-21 percent over Sanders and Warren, respectively.
Looking more closely at the polling methodology for each, we find that all three of these surveys have very low sample sizes, which means the error factor is high. The respective respondent universes are only between 424 and 440 people from which to derive a national trend. These numbers are more typically found in a congressional district or small state survey.
The YouGov poll (Oct. 20-22; 628 US Democratic likely voters) used a larger national sample and found a much tighter standing among the candidates, but with the prevalent Biden-Warren-Sanders order intact through a 24-21-15 percent result. In all of the aforementioned surveys, no other candidate reaches double-digit support.