While Trump took to Twitter to rant at Fox News, he was threatening MSNBC with a lawsuit.

On MSNBC's The Last Word With Lawrence O’Donnell, the host said basically that the Russian mob was co-signers for a loan that Trump took out with Deutsche Bank.

Trump’s personal attorney Charles Harder threatened NBCUniversal with a defamation suit over what was broadcast.

According to Harder's demand letter, "The Program and Tweet make the false and defamatory statements that 'Russian oligarchs' co-signed loans provided to Mr. Trump by Deutsche Bank, and described these 'co-signers' as 'Russian billionaires close to Vladimir Putin.'”

After making that statement, O’Donnell took to social media to try and put the toothpaste back in the tube. He tweeted out yesterday afternoon, "Last night I made an error in judgment by reporting an item about the president’s finances that didn’t go through our rigorous verification and standards process. I shouldn’t have reported it and I was wrong to discuss it on the air. I will address the issue on my show tonight."

Trump is notorious for defamation threats, but this may be the first formal one from a sitting president.

Of course, if NBC let the lawsuit move forward, it would open Trump up to a very interesting discovery process.

And that, I can assure you would bring in higher ratings than The Last Word With Lawrence O’Donnell.

Something to think about NBC, something to think about.