Democratic debates: 10 have qualified for the next debate

Castro earned a 2 percent share in a CNN poll released Tuesday, earning him a spot in the debate set for next month in Houston.

Castro will join nine others who have met polling and donor requirements for the next debate: former Vice President Joe Biden; Sen. Bernie Sanders, Vermont; Sen. Cory Booker, New Jersey; Sen. Kamala Harris, California; Sen. Amy Klobuchar, Minnesota; Sen. Elizabeth Warren, Massachusetts; Mayor Pete Buttigieg, South Bend, Indiana; Beto O'Rourke, former representative, Texas, and entrepreneur Andrew Yang.

Candidates had to meet more stringent requirements to be included in the September debate, including having 130,000 unique donors and registering at least 2 percent support in four national polls approved by the Democratic National Committee.

The debate is scheduled for Sept. 12 and 13 in Houston, though whether two nights of debate will be needed is unclear.

According to the rules set forth by the DNC at the beginning of the debate process, only 10 candidates will be onstage during a given debate. If an 11th candidate should qualify, the debate will likely be held over the two nights.

Candidates have until Aug. 28 to qualify for the debate. Should they qualify for the September debate, they will also qualify to be included in the October debate. The date of the October debate has not been announced.

If a candidate does not make the September debate, he or she has up until two weeks before the October debate to qualify.

Two other candidates – Rep. Tulsi Gabbard, Hawaii, and billionaire donor and impeachment advocate Tom Steyer – have both met the donor threshold to be included in the debate, but have not met the polling requirements.

Gabbard needs two polls to qualify and Steyer needs one.

Self-help author Marianne Williamson and Washington Gov. Jay Inslee have also met donor requirements, but neither has scored enough support in any poll to qualify.