(Video still via CNN)

The third presidential debate is over, and so should any remaining national debate over Donald J. Trump's fitness for the office.

He is a disaster.

Trump held strong, playing nice 'n' normal for 20 or so minutes, straining hard to use his indoor voice (and looking pitted and shiny, makeup-free).

3/3. #SheWon pic.twitter.com/jMIDESup7K

— Hillary Clinton (@HillaryClinton) October 20, 2016

Then, he got vicious, and remained snarky and petulant nonstop, allowing his blows to be overshadowed by problems of his own making: Saying he has not apologized to Melania over the groping claims, pretending all nine accusers' stories have been debunked, fantasizing that the Mosul campaign was designed to help Hillary, sticking to his story that he was against the Iraq War ... when he wasn't.

Clinton tells people to Google "Donald Trump Iraq" and ... pic.twitter.com/KMC1ycHUBG

— Kevin M. Kruse (@KevinMKruse) October 20, 2016

He simply can not not lie.

Most egregiously, he committed two I-think-fatal errors: He couldn't hold his tongue, interrupting Hillary after a mild zinger to seethe that she is a nasty woman; and his jaw-dropping decision to say he will not commit to accepting the results of the election.

The latter will be the takeaway from this debate, his last chance to stop his freefall and possibly regain any momentum.

He is not going to soar from this performance.