It was bad enough back in 2011 when Donald Trump began peddling the crackpot conspiracy theory that President Barack Obama was not a native-born American. But at least Trump was just a private citizen then.

By the time he tweeted last month that Obama had sunk so low as to “tapp [sic] my phones during the very sacred election process,” Trump was a sitting president accusing a predecessor of what would have been an impeachable offense.

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Trump went public with this absurd accusation without consulting the law enforcement and intelligence officials who would have disabused him of a conspiracy theory he apparently imbibed from right-wing media. After the FBI director debunked it, Trump held fast, claiming he hadn’t meant that he had been literally wiretapped.

Most people know by now that the new president of the United States trafficks in untruths and half-truths, and that his word cannot be taken at face value.

Even more troubling, though, is that much of his misinformation is of the creepiest kind. Implausible conspiracy theories from fly-by-night websites; unsubstantiated speculations from supermarket tabloids. Bigoted stories he may have simply made up; stuff he heard on TV talk shows.

The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive. — Donald J. Trump (@realDonaldTrump) November 6, 2012 In addition to winning the Electoral College in a landslide, I won the popular vote if you deduct the millions of people who voted illegally — Donald J. Trump (@realDonaldTrump) November 27, 2016

This is pathetic, but it’s also alarming. If Trump feels free to take to Twitter to make wild, paranoid, unsubstantiated accusations against his predecessor, why should the nation believe what he says about a North Korean missile test, Russian troop movements in Europe or a natural disaster in the United States?

Trump’s willingness to embrace unproven, conspiratorial and even racist theories became clear during the campaign, when he repeatedly told tall tales that seemed to reinforce ugly stereotypes about minorities. Take his now famous assertion that he watched thousands of people in “a heavy Arab population” in New Jersey cheer the collapse of the World Trade Center on 9/11, an astonishing account that no one has been able to verify. PolitiFact rated that as “Pants on Fire.”

Or his retweeting of a bogus crime statistic purporting to show that 81% of white homicide victims are killed by blacks. (The correct figure was 15%.)

On several occasions he retweeted white nationalists. (Remember the image of Hillary Clinton and the star of David, for instance?)

His engagement with, to put it politely, out-of-the-mainstream ideas has attracted some strange bedfellows. It may not be fair to attribute to his senior aide, Steve Bannon, all the views that were published on the controversial alt-right site Breitbart.com, of which Bannon was the executive chairman. But it is certainly fair to wonder why Trump has elevated to a senior West Wing position a man who has trafficked in nonsense, bigotry and rank speculation.

Of course it was widely hoped that when Trump came into office he would put the conspiracy theories and red-meat scare stories behind him. Perhaps the “lock her up” mantra and the fear-mongering about Mexican rapists and the racial dog whistles and the assertions about Ted Cruz’s father’s connection to Lee Harvey Oswald — perhaps all that was just part of a cynical bid for votes, and it would go away when the election was over.

“ He is allowing the credibility of his unimaginably powerful office to be exploited and wasted on crackpot ideas. ” Share this quote

But there’s no sign of that. Trump seems as willing to mouth off today as he was on the campaign — about wiretaps, inauguration crowds, fraudulent voters, you name it. And the problem with that is that he is no longer a blowhard TV personality or a raunchy guest on Howard Stern or a self-promoting real estate magnate or even a long-shot candidate for the Republican nomination. He’s now the president of the United States, and he is allowing the credibility of his unimaginably powerful office to be exploited and wasted on crackpot ideas that have been rightly discredited by politicians from both parties.

This is the fifth in a series.