WASHINGTON -- During the primary season, as Donald Trump's bizarre outbursts helped him crush the competition, I thought he was being crazy like a fox. Now I am increasingly convinced that he's just plain crazy.

I'm serious about that. Leave aside for the moment Trump's policies, which in my opinion range from the unconstitutional to the un-American to the potentially catastrophic. At this point, it would be irresponsible to ignore the fact that Trump's grasp on reality appears to be tenuous at best.

Begin with the fact that he lies the way other people breathe. Telling a self-serving lie -- no matter how transparent, no matter how easily disproved -- seems to be a reflex for him. Look at the things he has said in just the past week.

On Wednesday, at a news conference in Florida, Trump said he has never met Russian President Vladimir Putin. "I never met Putin, I don't know who Putin is," he said.

Last November, he claimed that he "got to know [Putin] very well because we were both on '60 Minutes.'" That made no sense; while the two men were featured the same evening on the CBS newsmagazine show, they were interviewed in different cities and would have had no interaction. But there's more: In 2014, speaking at the National Press Club, Trump said, "I was in Moscow recently and I spoke, indirectly and directly, with President Putin, who could not have been nicer, and we had a tremendous success."

So was he lying last week, when he was trying to deflect criticism of his admiring words for the Russian strongman? Or was he lying two years ago, when he was trying to convince everyone what a big shot he was?

Also within the week, Trump lied in complaining about the presidential debate schedule and its conflicts with professional football. He told ABC News' George Stephanopoulos, "I got a letter from the NFL saying, 'This is ridiculous. Why are the debates against -- ' because the NFL doesn't want to go against the debates."

The National Football League responded: "We did not send a letter."

Trump also lied about his interactions with the conservative billionaire Koch brothers. "I turned down a meeting with Charles and David Koch. Much better for them to meet with the puppets of politics, they will do much better!" Trump proclaimed Saturday on Twitter.

A spokesman for the Koch organization said no meeting with Trump was requested.

It is theoretically possible, I suppose, that Trump is telling the truth and everyone else is lying -- although in the case of the Putin relationship, it's Trump's word against Trump's. Or perhaps the lies about the NFL and the Koch brothers are little things. But he also lies about big things -- claiming, for example, that he opposed the Iraq War and the Libya intervention all along, when the record shows that initially he supported both. No, Trump is clearly a liar.

Also, he's alarmingly thin-skinned. Referring to critics who spoke at the Democratic National Convention, Trump said last Thursday that he wanted to "hit a number of those speakers so hard, their heads would spin. ... I was going to hit one guy in particular, a very little guy." Trump made clear Friday on Twitter that he was talking about "'Little' Michael Bloomberg, who never had the guts to run for president."

Bloomberg, a far wealthier New York billionaire, had belittled Trump's supposed strength -- his business acumen. In a tantrum of tweets, Trump charged that Bloomberg's last term as mayor of New York was a "disaster." Back when Bloomberg left office, however, Trump called Bloomberg a "great" mayor. Which is it, I wonder?

Finally, there's ample evidence that Trump is the worst kind of bully. Look at the way he reacted to the powerful Democratic convention speech by Khizr Khan, the father of a Muslim American soldier who was killed in the Iraq War.

Trump initially did not have the courage to respond directly to Khan. Instead he smarmily attacked Khan's wife, Ghazala, who had stood silently on the stage. "She was standing there. She had nothing to say. She probably, maybe she wasn't allowed to have anything to say. You tell me."

There's no need for me to defend Ghazala Khan, who spoke eloquently for herself in a Washington Post op-ed. But tell me: What kind of man has so little empathy for a grieving mother's loss? Is that normal? Is it healthy?

The presidency comes with far-reaching powers. Not everyone should be allowed to wield them.

(c) 2016, Washington Post Writers Group