So far there are 19 Democratic candidates that have announced.
https://www.nytimes.com/interactive/...andidates.html
I feel like Booker and Harris are establishment politicians that won't generate much interest other than from PACs and other establishment politicians.
Warren no longer is seen as the thorn in the side anymore and has had too many gaffes to beat Trump. Her star is fading. I feel the same can be said for O'Rourke. The more he talks the less competent he appears.
Sanders still excites a lot of people on all sides of the political spectrum but he needs to win the nomination first. Plus, he's old.
There are some one-note candidates like Yang, Moulton, Inslee.
Then there are some of the odder candidates (IMO) like Delaney, Williamson, Hickenlooper, Messam.
To me that leaves a field of Buttigieg, Castro, Gabbard, Gillibrand, Klobuchar, Ryan and Swalwell. My favorite of the bunch so far is Buttigieg but I wonder how broad his appeal is.
There could be some others yet to declare, like Biden, that would make an impact.