The mystery of yesterday’s vicious “adult day care” tweet was whether it was a one-off, essentially a shot across the bow from Corker warning Trump not to criticize him again, or a declaration of war, promising many more attacks for the duration of Corker’s lame-duck tenure in the Senate.

We appear to have our answer.

Looks like Corker’s going to take advantage of his electoral freedom to go full Bulworth on Trump going forward. Who benefits most from that, though? The GOP establishment or the populists who hate them?

Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee, charged in an interview on Sunday that President Trump was treating his office like “a reality show,” with reckless threats toward other countries that could set the nation “on the path to World War III.”

Mr. Trump poses such an acute risk, the senator said, that a coterie of senior administration officials must protect him from his own instincts. “I know for a fact that every single day at the White House, it’s a situation of trying to contain him,” Mr. Corker said in a telephone interview…

Without offering specifics, he said Mr. Trump had repeatedly undermined diplomacy with his Twitter fingers. “I know he has hurt, in several instances, he’s hurt us as it relates to negotiations that were underway by tweeting things out,” Mr. Corker said…

“Look, except for a few people, the vast majority of our caucus understands what we’re dealing with here,” he said, adding that “of course they understand the volatility that we’re dealing with and the tremendous amount of work that it takes by people around him to keep him in the middle of the road.”

He also claimed contra Trump’s tweets yesterday that Trump repeatedly offered to endorse him for reelection, an allegation that’s been made before: “I don’t know why the president tweets out things that are not true. You know he does it, everyone knows he does it, but he does.” If you can think of a prior case of a sitting senator laying into a sitting president from his own party as both a compulsive liar and an unstable crank whose impulsiveness threatens global war, let me know.

Again, though: Who benefits primarily from Corker going rogue on Trump? POTUS will rant and rave in the Oval Office and tie himself in knots over the fact that he has no leverage over Corker anymore — but so will McConnell and the Senate GOP, many of whom are facing tough races next year and will now be put on the spot by the media to either back Corker up or back Trump up. If you side with Corker, the Bannon brigades will cite it as proof that the Republican establishment really does hate Trump en masse and must be serially ousted in primaries. If you side with Trump, you’ll be excoriated by the press and you’ll leave your friend and Senate colleague Corker out on a limb, with no clue as to how he might react. What if Corker starts leaking to the media about what Republican Senate colleagues have said to him privately about Trump? I’m sure Ted Cruz, for instance, quietly agrees with every word Corker said in the Times interview. (If you doubt it, go watch him deliver his own nuclear attack on Trump’s character the week of the Indiana primary last year.) But Cruz is up for reelection in a red state and he’s already annoyed Trump fans by refusing to endorse POTUS at the convention. Siding with Corker might earn him a primary, or it might at a minimum mean Trump supporters staying home next November for Cruz’s race against Beto O’Rourke.

And then there are the Senate GOPers who won’t face voters again for years but still haven’t mustered the nerve to hit Trump hard as president yet — at least by name:

Rubio’s been tweeting scripture every morning for months, much of which often seems like a subtle (or not that subtle commentary) on the day’s Trump news. Presumably the tweet above is a wink of support for Corker. Which makes sense: Rubio’s most famous criticism of Trump during the presidential primaries — apart from the size of his hands, I mean — was that he was too unbalanced to be trusted with the nuclear codes, the same critique Corker’s offering now. Of course, Rubio eventually went on to endorse Trump while, er, never quite retracting his “too dangerous for nukes” accusation against him. But then, nearly all Senate Republicans are compromised. Bob Corker himself was fast out of the gate after the Indiana primary last year in urging anti-Trump Republicans to calm down and adjust to the idea of Trump receiving the nomination, even as conservatives were trying to put together a means to block him at the convention. Corker also kept his mouth shut nice and tight about Trump’s foibles when he was in the running to be named secretary of state. All of the personality defects to which he now objects in Trump were on full display last year when Corker was waving his pom-poms for POTUS because he had something to gain from their alliance. Hopefully the media will remind him of that from time to time as he does his DefJam Comedy Tour at Trump’s expense over the next 15 months.

Two clips for you on this topic via Mediaite from this morning’s “Fox & Friends,” in order of increasing surrealism. First the hosts slap Corker for being “disrespectful” to the president on Twitter, as though the guy in the White House right now didn’t become a political force on the right by demagoging Obama’s natural-born status day after day on the same platform. Then Kellyanne Conway, Trump employee, appears to marvel at how “incredibly irresponsible” it is for Republican leaders like Corker to use Twitter to insult people. What?