The Democratic National Committee says it is making the move “at the request of both campaigns and out of an abundance of caution.”
DNC Communications Director Xochitl Hinojosa says local public health officials had advised that the debate could continue as planned.
In addition to the cancelation of the live audience, there will be no press filing center for the media in Phoenix or a "spin room" where candidates or surrogates huddle with members of the media for post-debate interviews.
Hawaii Rep. Tulsi Gabbard, who is still in the race, didn’t qualify for the upcoming debate under the latest set of rules.
CNN and Univision will air the debate on television.