Kellyanne Conway's Wednesday night interview on Fox News was going to be a big deal.

Fox promoted it ahead of time as the administration's first on-camera reaction to the news about former FBI Director Robert Mueller's appointment as special counsel overseeing the federal government's Russia investigation.

But the White House abruptly canceled Conway's appearance, causing Fox host Tucker Carlson to fill the air time by discussing the cancellation.

The back-and-forth illustrated the Trump administration's ongoing struggle to keep up with the news cycle and supply guests for television news programs.

"She canceled about an hour before airtime," Carlson said.

Conway told CNNMoney that she was with the president and other administration officials "until after hit time."

White House communications director Mike Dubke's team "says he canceled it knowing I was still in there indefinitely," Conway said.

The change was notable because no members of President Trump's inner circle appeared on TV Wednesday. Conway was going to be the first.

With the White House facing a deepening crisis of credibility and questions about possible obstruction of justice, the interview was going to be highly newsworthy.

Related: Does anyone in Trump's White House have credibility?

Carlson, the host of "Tucker Carlson Tonight," said it was the White House's idea to have her on his show.

"We had booked her, at their request, by the way," Carlson said on the air. "We don't often have people from the administration on, but they said, 'We want to send over Kellyanne Conway.' 'Great.' And then, not long before air, they canceled it, for reasons that weren't exactly clear."

Carlson's substitute guest was Matt Schlapp, the chairman of the American Conservative Union.

Carlson said to Schlapp, "I think a lot of descriptions in the press about what's going on at the White House are false or they're animated by the hate that the press has for Trump, which is totally real. But it does seem a little chaotic over there, I gotta be honest with you. Is it as chaotic as it seems?"

Schlapp, who said he was at the White House earlier in the day, said the atmosphere is more "tranquil" than it seems from the outside.

Television bookings are usually arranged through the White House press shop. Late Thursday, after the cancellation dust-up, Conway said she followed up personally with Carlson.

According to a Fox spokeswoman, Conway was originally booked in the afternoon, before the Justice Department's 6 p.m. announcement about Mueller.

The White House yanked the interview around 7:15 p.m. With Carlson's show set to begin at 8 p.m., producers kept trying to convince her to honor the booking.

That's why Fox continued to promote the interview right up until 8 p.m.

But the White House would not reconsider.

On the air, Carlson said he called up the White House before airtime to ask about the flip-flop. He said: "The explanation, I think it was sincere, was, 'We had no idea this was happening, we are trying to figure out how to respond to it.'"

Later in the hour, Fox's White House correspondent John Roberts said he surmised that the administration "just wants the president's statement to speak for itself."