Bullock will replace U.S. Representative Eric Swalwell, who dropped out of the 2020 White House race earlier this month. The other 19 candidates will be the same as the participants in the first round of Democratic debates last month in Miami.
Left out of the July 30 and July 31 debates will be U.S. Representative Seth Moulton of Massachusetts, former U.S. Senator Mike Gravel of Alaska, billionaire environmentalist Tom Steyer, former U.S. Representative Joe Sestak and Wayne Messam, the mayor of Miramar, Florida.
The lineup of 10 candidates for each night will be determined in a live drawing on Thursday night on CNN, which will air the debates.
The Democrats are competing for the nomination to challenge Republican President Donald Trump in 2020.