To qualify, candidates had to be on enough state ballots to reach 270 electoral votes, or enough to win. They also had to receive at least 15% in four separate national polls, among those specified by the network.

Kennedy had reached that threshold in three polls, but was on the ballot in only 10 states, short of the 270 electoral votes, according to NBC News. The Kennedy campaign had said that it had enough signatures in 23 states, with 310 electoral votes. But those signatures still need to be verified by state elections officials.

Kennedy will have more time to qualify for the next presidential debate, scheduled for Sept. 10. ABC News is hosting that debate with similar criteria to CNN’s guidelines.

The last independent candidate to participate in a general election debate was Ross Perot, who took part in the 1992 debates along with Bill Clinton and George H.W. Bush. Perot ran again in 1996 but did not qualify to the debates that cycle.