Don Lemon at a CNN event at the American Museum of Natural History in New York City in 2014. (Andrew H. Walker/Getty Images)

CNN’s Don Lemon and Fox News’ Bill O’Reilly have found a way to turn allegations about the “unmasking” of members of President Trump’s campaign and transition teams into a story about each other.

Their spat started late Monday, when Lemon, host of “CNN Tonight,” ran a segment saying he wouldn’t “aid and abet” Trump’s claims that the Obama administration had spied on him. In the same segment, Lemon defended former national security adviser Susan E. Rice against suggestions that she leaked the identities of Trump surrogates mentioned in foreign surveillance intelligence reports for political purposes.

Rice has denied that she sought anyone’s name for political reasons, and has called claims that she leaked identities “completely false.”

“On this program tonight, we will not insult your intelligence by pretending otherwise,” Lemon said, “nor will we aid and abet the people who are trying to misinform you, the American people, by creating a diversion.”

O’Reilly responded Tuesday afternoon by tweeting that Lemon “refuses to cover” the allegations against Rice. He ran a clip of Lemon’s commentary on “The O’Reilly Factor” website, saying Lemon had “declared his show a Rice-Free Zone.”

It escalated from there.

Lemon fired back by bringing up the wave of sexual harassment accusations against O’Reilly that have come to light in the past few days. O’Reilly’s show is facing an exodus of advertisers after a New York Times investigation over the weekend revealed five women have received a combined $13 million in settlements stemming from complaints about his conduct.

“False. I did not refuse to cover the story,” Lemon tweeted. “But I did cover your sexual harassment allegations. Did you?”

Of course, Lemon had indeed covered the allegations against Rice — though perhaps not in the way O’Reilly wanted — and he went out of his way to say so on his show Tuesday night.

“Normally I wouldn’t address this, but he has a lot of followers and people are believing alternative facts now,” Lemon said of O’Reilly. He went on to play several clips of panelists talking about Rice having unmasked members of Trump’s team.

“So, Bill, we have covered the Susan E. Rice story, we did it for a long time on this program last night, and tonight we’re going to cover it again,” Lemon said.

In the panel discussion that followed, Lemon doubled down on his defense of Rice, arguing there was no evidence she acted improperly by seeking the names of Trump surrogates concealed in intelligence intercepts.

A subsequent panel on “CNN Tonight” delved into the sexual harassment allegations against O’Reilly, which Lemon had previously covered on his show. As of Tuesday night, at least 11 advertisers had withdrawn or moved ads from the “O’Reilly Factor,” among them leading car and pharmaceutical companies, as The Washington Post’s Paul Farhi reported.

There was a moment in what now seems like the distant past when Lemon and O’Reilly found some common ground. In a 2013 discussion about race relations in the United States, O’Reilly tried to blame violence in black communities on “disintegration of the African American family.” Lemon, who is black, surprised viewers when he took O’Reilly’s side.

“Bill’s got a point,” he said on CNN. “In my estimation, he doesn’t go far enough.”

Presidential candidate Donald Trump and Fox News host Bill O'Reilly had an awkward exchange after the GOP debate March 3. It's not the first time the two have clashed, but they also seem pretty friendly at times too. (The Washington Post)

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