For the third debate, September 12-13 in Houston: 
---met both criteria (fund-raising, polls) 
Biden 
Buttigieg 
Harris 
Sanders 
Warren 
Booker 
O'Rourke 
Klobuchar 
Yang 
---met fund-raising criteria only 
Castro 
Gabbard 
---met no (fund-raising, polls) criteria yet 
Steyer (no donors reported yet) 
Gillibrand (>100,000 donors on August 6) 
Hickenlooper (~13,000 donors on July 2) 
Bennett (~28,000 donors on June 30) 
Bullock (~17,000 donors on June 30) 
de Blasio (~7,000 donors on June 30) 
Inslee (>110,000 donors on August 5) 
Messam (no donors reported yet) 
Moulton (~14,000 donors on June 30) 
Ryan (~13,000 donors on July 12) 
Sestak (no donors reported yet) 
Williamson (116,435 donors on August 7) 
https://en.wikipedia.org/wiki/2020_Democratic_Party_presidential_debates_and_forumsAll who qualify for the above (third) debate automatically go to the fourth debate in October.