I thought Trump’s first nuclear exchange would be with Kim Jong Un. He’s unpredictable!

He has ample reason to be irritated with Corker. Corker’s the guy who begged him last month to go to Alabama and stump for Luther Strange, putting Trump on the wrong side of his base and setting him up for embarrassment when Roy Moore won easily. Corker’s also been taking potshots at him, questioning his “competence” in August and then slamming him again a few days ago when he said Mattis, Kelly, and Tillerson are helping to “separate our country from chaos.” He doesn’t think much of Trump, clearly. And Trump doesn’t think much of anyone who doesn’t think much of Trump.

Even so, this may be his single stupidest tweetstorm as president.

https://twitter.com/realDonaldTrump/status/917026789188399105
https://twitter.com/realDonaldTrump/status/917029060471152640
https://twitter.com/realDonaldTrump/status/917030148867682304

That drew this reply, which is as nasty a shot at POTUS as any Senate Republican has taken since January 20th. Not even Jeff Flake, Trump’s most stalwart critic, has gone for the throat quite this eagerly:

It's a shame the White House has become an adult day care center. Someone obviously missed their shift this morning.

— Senator Bob Corker (@SenBobCorker) October 8, 2017

That’s what a lame duck looks like when his wings are fully extended. Now that Corker has nothing to lose electorally by challenging Trump, I wonder if he plans to keep this up over the next 15 months, using his freedom to say what the rest of McConnell’s caucus is thinking but dares not say themselves.

Corker is saying publicly what other GOP senators and bigwigs have been saying privately — for months. https://t.co/ES7jHiW9QA https://t.co/srJwmrwgaA

— Evan Osnos (@eosnos) October 8, 2017

Anyway, let’s do some first-grade math. McConnell has 52 votes. The party’s going to *try* to pass tax reform via reconciliation, which means he needs 50. Susan Collins and Lisa Murkowski are perennially tough “gets” in the center; Rand Paul is similarly uncompromising on the right. McCain, who’s also almost certainly in his last term, has spiked health-care reform not once but twice and obviously enjoys sticking it to Trump, for understandable reasons. Now here’s POTUS doing everything he can to alienate another must-have Republican in Corker, who’s already iffy on tax reform if it raises the deficit. Why would McConnell even bother to pursue a bill? It’s dead on arrival, thanks in part to Trump’s vain need to avenge personal insults publicly.

But it gets worse. Corker’s also the chairman of the Senate Foreign Relations Committee. The Foreign Relations Committee will be the main body tasked with figuring out what to do about the Iran deal once Trump decertifies it this month. The administration’s reportedly hoping Congress will hit Iranian entities like the Revolutionary Guard with targeted sanctions; having an ally in the chairman of the Committee would make that task much easier. Having an enemy in him will make it less predictable. Trump’s 100 percent right that Corker was complicit in getting Obama’s Iran nuclear deal through the Senate but trying to shame him publicly about that now as part of an all-out attack on Corker won’t make the decertification process easier. On the contrary.

One more thing. People are whispering to the media that Trump’s tweets simply aren’t true. He allegedly did offer to endorse Corker, as recently as last week:

Also Trump called Corker early last week and asked him to *reconsider* his decision to retire and said again he'd endorse him, per source

— Manu Raju (@mkraju) October 8, 2017

Right, right, that could just be Team Corker making stuff up to save face and embarrass Trump after POTUS’s Twitter broadside against him this morning. But the claims that Trump offered to support him for reelection aren’t recent. The AP reported it three weeks ago.

In lieu of an exit question, read this prescient AP story published just this morning, a few hours before Trump’s tweets, speculating that Corker will be a loose cannon now that he’s declared his intention to retire. “Sen. Bob Corker is always one to speak his mind,” noted author Richard Lardner, “and the Tennessee Republican’s new free agent status should make President Donald Trump and the party even more nervous.” Not nervous enough!

.@SenBobCorker: "I think Sec. Tillerson, Sec. Mattis and Chief of Staff Kelly are those people that help separate our country from chaos." pic.twitter.com/NjuRX59s6A

— CSPAN (@cspan) October 4, 2017