What happened on that stage needs to be made undeniably clear to every American citizen who isn't hopelessly lost in denial. (And clearly, many are.)
That job will fall, in part at least, to the American press, who will find itself in the uncomfortable position of calling a spade a spade, with none of the usual recourse to false equivalence or "both sides with equal weight" coverage.
CNN's Anderson Cooper led the way with his immediate - and memorable - live assessment: "You have been watching perhaps one of the most disgraceful performances by an American president . . . ."
And others followed suit.
James Fallows of the Atlantic quickly wrote a tough piece: "Never before have I seen an American president consistently, repeatedly, publicly, and shockingly advance the interests of another country over those of his own government and people."
Clearly, not all will be up to the challenge. That, too, was obvious in the moment.
On Fox News, the Trump-favoured White House correspondent John Roberts (a very recent beneficiary of White House approval) tried to explain Trump's words: "He's developed a little bit of an inroad to Putin . . . and he doesn't want to spoil that by saying he doesn't believe Putin."
That Fox News "scored" two Trump interviews - one with Sean Hannity and one with Tucker Carlson - is completely predictable, especially with former Fox honcho Bill Shine as the new White House communications tsar.
When it comes to Fox and Trump, the answer to the lyric Will the Circle Be Unbroken is abundantly obvious.
But for the reality-based press, the job will require clarity and moral force, in ways we're not always all that comfortable with.
Just as it took months to come to terms with referring to Trump's endless falsehoods (when they are clearly intentional) as "lies," we need to get out of our ingrained habits in order to tell this story clearly.
Some signs were encouraging. In the Post, Aaron Blake's analysis told it plainly: "Trump's news conference with Putin was everything Putin could have dreamed" read the headline.
The lead headline on the Guardian US website got right to the point, too: "Trump condemned as treasonous after press conference with Putin."
But the press' default position is to normalise, to represent various points of view with equal weight, to be swayed by the pomp of the presidential office. To act like everything is just as variation on a theme - something we've seen before but maybe in a slightly paler shade.
That's not good enough.
Journalism, writ large, can be proud of AP's Jon Lemire and Reuters' Jeff Mason, who asked well-honed, incisive questions and asked them in just the right way. (Historical note: Lemire, back in October of 2016, was thrown out of a room by Trump's campaign people, as the candidate called him a "sleazebag" for asking tough questions about sexual misconduct claims against him.)
Mason and Lemire held Trump's feet to the fire.
If any such pride is to continue in the hours and days ahead, news organisations need to step up to the job of driving home to American citizens the larger picture, too.
It's not enough to offer such pallid assessments as those we've heard too often, that "this is outside the norm," or "there's little precedent for what we're hearing."
Clarity of purpose and moral force are called for. They are not always in ample supply by a too-docile press corps.
Fallows called the press conference a "moment of truth" for Republican lawmakers.
So, too, for American journalists.
