Trump’s goading succeeded in ripping off Biden’s “nice guy” mask and forcing him to fight in the ­gutter.

Instinctively, or deliberately, the president engaged in a winning fighting strategy deployed by the best national rugby team in the world, New Zealand’s All Blacks. They come out hard in the first phase of the game, using sheer brute violence to probe their opponents’ weaknesses. It’s not pretty but it’s effective if your goal is to win.

So if Biden gives it his best effort in the next two debates rather than using Trump’s lack of decorum as an excuse not to engage, then you’ll see the president calibrating his ­attacks to zero in on Biden’s vulnerabilities.

Sure, the debate was a chaotic mess. But the emotional takeaway was this: In a turbulent world with circling predators like Chinese President Xi Jinping, who do you want defending America? An aggressive pit bull who will do anything to win, or a smirking milquetoast hurling schoolyard insults.