President Trump in a tweet on Monday promoted a “Fox News” interview with lawyer Alan Dershowitz defending him against possible obstruction of justice charges as “must watch” television.

“A must watch: Legal Scholar Alan Dershowitz was just on @foxandfriends talking of what is going on with respect to the greatest Witch Hunt in U.S. political history. Enjoy!,” the president wrote on Twitter.

Dershowitz appeared on “Fox and Friends” to say Trump had every right to tell then-FBI Director James Comey to drop the investigation into former national security adviser Michael Flynn.

“You cannot charge a president with obstruction of justice for exercising his constitutional power to fire Comey and his Constitutional authority to tell the justice department who to investigate, who not to investigate,” he said. “We have precedents that clearly establish that. ”

Flynn pleaded guilty on Friday to lying to the FBI about his contacts with Russian ambassador Sergey Kislyak and is now cooperating in special counsel Robert Mueller’s investigation into Moscow’s meddling in the 2016 election.

A tweet posted on Trump’s account Saturday acknowledged that the president knew Flynn had lied to the FBI before he reached out to Comey in February to end the investigation.

“I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies,” the Twitter post said. “It is a shame because his actions during the transition were lawful. There was nothing to hide!”

Later, Trump’s private lawyer, John Dowd, admitted writing the tweet and said it was his “mistake.”

“For obstruction of justice by the president, you need clearly a legal act,” Dershowitz said.

Comey, who was fired by Trump in May, testified in June that the president told him, “I hope you can see your way clear to letting this go, to letting Flynn go,” during a White House meeting on Feb. 14, a day after Flynn’s ouster.

Trump fired Flynn after news reports revealed he lied to White House officials and Vice President Pence about his contacts with Russian officials.