Donald Trump displayed an excellent version of the stern squint in the presidential debate. Many of us men are familiar with this expression, because we practice it at age 13 in the hope that it will impress girls. It doesn’t, and we grow out of it — most of us, anyway.

Hillary Clinton wears a patient smile, the expression of every woman who has calmly suppressed irritation while being harangued by a boor on topics he knows nothing about. Sadly, women never have the opportunity to retire this expression because it is constantly needed, or so my wife tells me.

What is thrilling is that Trump’s boorishness may be catching up to him.

Trump has advocated policies that are confused or senseless — deporting 11 million undocumented immigrants en masse, banning Muslims from entering the country, undermining NATO, slashing taxes on billionaires while raising them on single parents, capitulating to Russia on Crimea — yet these don’t get him into deep political trouble. Instead, his vulnerability seems to be something more elemental: He’s a jerk.