you do see these outliers once in a while with sanders leading, and it's what the media is picking up on, probably because the narrative of biden running flat for two years is kind of boring and it needs click bait....

but, even in these polls, it's never that sanders is rising. i mean, he might be up a point or two, in a survey with a 5% margin of error, or something. but, the reason he ends up on top in these polls is that biden's support ends up scattered. these polls don't just have sanders on top with 25%, and biden sinking into the teens. these are also the polls with klobuchar sitting at 9%, and yang or steyer at 7% or 8%.

what if these polls are right? well, it would be kind of a disaster for the party to have sanders win the first two or three states with 20-25%, each and end up with six or seven other candidates running over 10%. but, in the long run, it doesn't help sanders for all of these other candidates to split a couple of states, if they just realign with each other, in the end. if the best polls that sanders can find have him ahead with 23%, and klobuchar hanging on with 10+%, he's going to get leapfrogged after a few states, anyways. these polls would suggest that a weak early showing by biden could give buttigieg or klobuchar a serious bounce.

but, these polls probably aren't right.

biden is probably coasting quite comfortably, and set to sweep.