After Trump's Twitter tantrums yesterday — calling for the jailing of a political opponent and bragging his nuclear button is bigger than North Korea's — CNN used its powerful platforms and people to suggest the president is mentally unstable.

The big picture: 2018 is off with a familiar bang, with the president trashing the media, and the media trashing him.

• Jake Tapper started his 4 p.m. show, "The Lead": "President Trump is kicking off 2018 by going on Twitter, blasting Democrats, calling for a political opponent to be thrown in jail, demanding a potential witness be investigated, and praising himself. So, no New Year's pivot, apparently."
• Brian Stelter opened his late-night media newsletter, Reliable Sources (which had the subject line "Trump's fitness"): "There's a word for this. Madness."
• Stelter on "Anderson Cooper 360": "What would we say if the leader of Germany or China or Brazil posted tweets like Trump's? How would we cover it? We'd say: That person is not well. We'd wonder whether that person is fit to hold office."
• And a banner on a special 10 p.m. Tapper edition asked: "ARE WE CLOSER TO NUCLEAR WAR THAN EVER?"
• Tapper: "None of this [is] normal, none of this [is] acceptable, none of this [is] frankly stable behavior."

Why it matters: Trump has been known to watch CNN at that hour, and Stelter ended his item: "Was Trump watching?"