Nate Silver looking at the data for Debate Qualification for the Dems . (sorry for the formatting - looks better in the link provided):
Which candidates are good bets to make the third debate?
CANDIDATE QUALIFYING POLLS* UNIQUE DONORS NATE’S ASSESSMENT
Sanders 9 525,000 as of 3/31 Almost certain
Warren 9 135,000 as of 3/31 Almost certain
Harris 9 138,000 as of 3/31 Almost certain
Biden 9 96,926 as of 4/26 Almost certain
Buttigieg 8 158,550 as of 3/31 Almost certain
O’Rourke 9 163,000 as of 3/31 Almost certain†
Klobuchar 8 65,000+ as of 5/3 Probable
Booker 8 65,000+ as of 5/3 Probable
Yang 1 110,000 as of 5/29 Tossup
Castro 2 65,000+ as of 5/3 Tossup
Gabbard 1 65,000+ as of 4/10 Tossup at best
Gillibrand 1 <65,000 Tossup at best
Inslee 0 65,000+ as of 5/24 Tossup at best
Hickenlooper 1 <65,000 Tossup at best
Williamson 0 65,000+ as of 5/9 Leaning against
Ryan 1 <65,000 Lots of work to do
Bullock 0 <65,000 Lots of work to do
Delaney 0 <65,000 Lots of work to do
Swalwell 0 <65,000 Lots of work to do
de Blasio 0 <65,000 Lots of work to do
Bennet 0 <65,000 Lots of work to do
Moulton 0 <65,000 Lots of work to do
https://fivethirtyeight.com/features/silver-bulletpoints-whos-in-danger-of-missing-the-third-debate/