By Jon Keller

BOSTON (CBS) – Moments after the migraine headache masquerading as the first presidential debate lurched to a merciful end, one cable TV talking head summed it up succinctly if inelegantly: “that was a s—show.”

Moderator Chris Wallace of Fox News is getting a ton of grief for losing control of this mess early on and never really recovering, and he deserves it. When it wasn’t a totally incoherent shout fest, it degenerated into the one thing a “debate” should never become, a joint interview by an intrusive journalist.

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But Wallace is a sidebar. In a way, the event was a dead-on depiction of the degraded state of our political discourse, schoolyard insults and useless lip-flap worthy of a Twitter comment thread but not of a presidential debate.

I pity the undecided voters who tuned in hoping for some clarity. When the TV ratings come out Wednesday I bet they show a quick drop off as the debacle dragged on.

But like a shovelful of toxic sludge that yields a few quarters under an aggressive rinse, there were a couple of moments where content snuck through.

Trump momentarily shut off his firehose of vituperation to point out several of his signal achievements, a prison reform bill which drew bipartisan praise and a cascade of judicial appointments which didn’t. In the hands of a political leader interested in framing an actual governing philosophy, those could be interesting bookends.

And Biden did well when he lectured Trump on how the suburbs in particular and the country in general have changed to a more racially- and culturally-diverse model, and suggesting that “law and order” is only achieved when “people are treated fairly.”

Biden faltered at times, a failing often obscured by the president’s incessant braying. And some undecided voters won’t like his references to the president as a “clown,” even though the object of that taunt was working hard to earn it.

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But Biden likely emerged from the wreckage with an edge because of the moments when he looked right into the camera and expressed empathy with the voters and concern with their problems. The best Trump could manage was whining about how mistreated he’s been by [fill in critic here].

If Tuesday night’s “s—show” served any purpose beyond boosting Aleve sales, it was as an allegory for the fatal flaw of the Trump presidency.

As former GOP Sen. Rick Santorum, usually a reliable Trump toady, put it afterwards: the president was guilty of “overdoing it.”

So what happens next?

There are two more of these scheduled. I can’t imagine how much appetite there is among the public for even one more, let alone two more, forget about the vice presidential debate.

It wouldn’t surprise me if this was both the first and last debate of this presidential cycle.

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It was certainly hands down the worst presidential debate that I’ve ever seen.

Jon Keller