So much data, so little time! Probably the single thing you should be sure to look at is the RCP rolling average of candidate preference. Right now, Biden’s still ahead of course with almost twice the support of Sanders and Warren, who are now quite close in the polling average. Harris is a fairly distant fourth.
But also worth paying attention to are several media outlets who are starting to release data from their polls in graphical, cumulated form with interesting internal demographic trends. Politico, for example, has some nice material up from the Morning Consult poll. These data have Sanders still leading Warren by a significant amount, though they do have Warren gaining ground as pretty much every other poll does.
Some noteworthy internals here is that Sanders and Biden are neck and neck among Hispanics, while Biden has roughly twice the level of support of Sanders among blacks. And, as the polling feature notes, “Warren leads among the educated and rich, Sanders among the uneducated and poor”. There is also an interesting chart showing how incredibly white Buttigieg’s support is.
The Economist has even better visuals using YouGov data. For whatever reason, Warren seems to run particularly strong in these polls, nosing ahead of Sanders in recent data. The internals give Biden a slight lead among Hispanics by nearly four times the level of Sanders’ support among blacks. Biden runs ahead of Sanders and Warren among those with high school or less or some college, while Warren is the leader among both four year college graduates and those with postgraduate education.
Finally, Warren is the leader among those being at least considered by voters, regardless of who their first choice is. Among those whose first choice is specifically Biden, Sanders or Harris, Warren gets the most “consider” designations.