For a moment during Wednesday night's presidential debate in Las Vegas, Donald Trump completely proved the point Hillary Clinton was trying to make about him.

Specifically: That he's a sore loser who thinks any loss is due to foul play.

Let's go to the tape:

CLINTON: There was even a time when he didn't get an Emmy for his TV program three years in a row and he started tweeting that the Emmys were rigged against him.
TRUMP: Should have gotten it.
(LAUGHTER)
CLINTON: This is — this is a mind-set. This is how Donald thinks. And it's funny, but it's also really troubling.

Point, Clinton.

And to be clear, she was treading on pretty fertile ground here. Trump often complains about being wronged when he doesn't win. It's a pattern.

The most poignant example right now, of course, is the presidential election. With the latest polls showing him down big, Trump has taken to alleging massive yet-to-happen voter fraud and a media conspiracy against him. In the highest-profile moment of Wednesday night's debate, he declined to say whether he would accept the results of this election as legitimate.

“I will look at it at the time,” Trump said, repeating the phrase twice and adding: “I'll keep you in suspense, okay?”

But if history is any indication, Trump will not accept that his loss was fair.

The Emmy example that Clinton cited — points for research — is a telling one. Trump did indeed tweet repeatedly that he had been wronged.

The Television Academy, which runs the Emmys, on Wednesday night responded to Trump's renewed claim to have been robbed this way:

But this is par for the course for Trump.

In a particularly remarkable example from Post reporters Michael Kranish's and Marc Fisher's book on Trump this year, the Republican nominee reportedly objected to a study-mate having scored higher on a chemistry test, alleging cheating:

And then there was the 2012 election, in which Trump's preferred candidate, Mitt Romney — more recently, a Trump antagonist — was supposed to have been robbed.

“He lost the popular vote by a lot and won the election,” Trump tweeted, despite President Obama's having won the popular vote by several points. “We should have a revolution in this country!”

There was also the “rigged” GOP establishment in the primaries — even at a time when Trump was on his way to the nomination.

“The bosses are trying to run it,” he told CNN. “It’s a rigged party. The bosses want to pick whoever they want to pick. The voters wouldn’t stand for it.”

Despite his campaign's assurances that he would accept the results of the election, Trump has made clear that's far from a foregone conclusion.

And from Trump, that should not really be a surprise.