This is a good quote from Mediate
Following the interview, Baier blamed Harris’s team for the lack of time.
“We were supposed to start at 5 pm. This was the time they gave us,” he said. “Originally we were going to do 25 or 30 minutes, they came in and said, ‘Well, maybe 20.’ So it was already getting whittled down, and then the vice president showed up about 5:15. We were pushing the envelope to be able to turn it around for the top of six o’clock, so that’s how it started, and I could tell when we started talking that she was going to be tough to redirect without me trying to interrupt.” He concluded, “I had a lot of other questions.”
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So all things said, the "Fox needed to cut the interview to air it unedited at 6pm" doesn't make sense, because they had about another 15 minutes they could've kept the interview going, even with Harris' late arrival.