Donald Trump. (Mike Segar/Reuters)

Tuesday marks four weeks until the 2016 election. And the Republican presidential nominee is in the midst of blowing up his own party.

The news came — as it so often does with Donald Trump — via Twitter.

Trump followed that tweet with this one:

And this one:

Let's stop for a second. This is the Republican presidential nominee. Attacking his own party. Promising to teach his party leaders a lesson. Pledging to take the “shackles off.”

I've spent the better part of the past two decades covering politics — day in and day out. And, I can say without hesitation I have NEVER seen anything close to this. And I expect I never will again.

Republicans knew that this version of Trump — angry, cornered, vengeful, selfish — was always a possibility when they made the decision to line up behind him rather than attempt complicated measures to unseat him at the party convention. Trump had shown his petulance and I'll-just-take-my-ball-and-go-home-ism during the primary season whenever things weren't going his way. He would turn on Republicans who weren't for him, attacking them as losers or out of touch with the party's voters — or both.

But, there was a belief — it appears to be more of a blind hope in retrospect — that Trump could be managed, that he could be brought to heel either by the likes of Speaker Paul D. Ryan and Senate Majority Leader Mitch McConnell or by campaign managers Paul Manafort and/or Kellyanne Conway. That Trump could be made to understand that it was about more than him, that the entire party depended on him running a credible and serious campaign.

Back in June, as he sought to assure the party amid a self-inflicted controversy regarding Judge Gonzalo Curiel, Trump uttered these words: “I understand the responsibility of carrying the mantle. I will never let you down.” That speech, as I wrote at the time, was Trump's transparent attempt to say to Ryan, McConnell and lots of other skittish Republicans that he got it — he understood he needed to be good not just for himself but for the broader GOP.

It was clear even then, however, that Trump was saying what someone else had convinced him he needed to say — and that it wasn't what he really believed. And, in the end, the real Trump always broke through. He got rid of Manafort, a move seen as Trump reestablishing his renegade personality at the heart of the campaign. Conway appeared to hold sway with Trump for an extended period of time this summer — a period which coincided with his rise in the polls — but now it's quite clear that the campaign manager, chief strategist, message guru and pollster is Trump.

What appears to be happening is the Breitbart-ization of Trump's campaign, adopting a strategy of full-on attack against everyone who doesn't see the world as he does — including Republicans. (That move isn't totally out of the blue. Breitbart chief Stephen Bannon is a close Trump adviser.) Trump is effectively turning the guns on his own troops, a move that might be personally satisfying to him but that will result in near-certain carnage for lots of Republicans.

The promise to be unshackled means that this is going to get worse for Republicans. Maybe far worse. Trump will undoubtedly “go there” more often against Bill Clinton — as he did in the second debate — but will also do everything he can to embarrass Republican politicians who he believes have betrayed him (and their constituents). People I talked to over the weekend said the election for Republicans seemed headed for an every-man-for-himself mentality. But, it might be even worse than that now. You can try to run from Trump but (a) it might not work since we are so close to the election, and b) there's no promise that Trump will let you do it without attacking you by name.

This is an absolute worst-case scenario for Republicans. Had Trump turned against them months ago — or had his poll numbers dipped then as they have now — extricating themselves from the dumpster fire might have been painful, but it was possible. Now it's almost certainly too late to do any real distancing from the nominee even as he is promising more unpredictability and more intraparty attacks.

It's unclear how badly Trump can hurt his chances or those of his party downballot. But, the disaster scenario — an electoral college wipeout, losing the Senate and the House — now has to be on the table.