Donald Trump

Republican presidential candidate Donald Trump speaks at the Williston Basin Petroleum Conference, Thursday, May 26, 2016, in Bismarck, N.D. (AP Photo/Charles Rex Arbogast)

It was a moment so Donald Trump in its Trumpiness that if someone other than Donald Trump had said it, it would have been dismissed out of hand as the ranting of a conspiracy-obsessed crackpot.

In a recent interview, the Republican presidential frontrunner ventured forth from the fever swamps of the Web, where the darkest and most fetid of conspiracy theories still flourish, to trot out the tired (and long-discredited) theory that Bill and Hillary Clinton were somehow responsible for the death of former White House counsel Vincent Foster in 1993.

Foster had "had intimate knowledge of what was going on," he told The Washington Post. "He knew everything that was going on, and then all of a sudden he committed suicide ... I don't know enough to really discuss it ... [but] I will say there are people who continue to bring it up because they think it was absolutely a murder."

Never mind that multiple investigations have concluded that Foster tragically took his own life as a result of a battle with depression.

As he escalates his criticism of the Clintons' personal lives and the White House scandals of the 1990s - a rich and deep vein, to be sure - Trump found an angle of attack and stuck with it.

"It's the one thing with her, whether it's Whitewater or whether it's Vince or whether it's Benghazi. It's always a mess with Hillary [Clinton]," Trump said in a recent interview, The Washington Post reported.

Of course, Trump was smart enough to insulate himself. He wasn't the one who was saying it.

It was out there ... in the world, where people were talking about it. And he'd never bring it up first.

"Well, the question was asked about Vince Foster, and it was asked of me: 'What do you think of Vince Foster.' I really know nothing about the Vince Foster situation, haven't known about it, and somebody asked me the question the other day and I said that a lot of people are very skeptical as to what happened and how he died," Trump said during a news conference in Bismarck, N.D. "I know nothing about it. I don't think it's something that, frankly, really, unless some evidence to the contrary of what I have seen comes up, I don't think that it's something that should be part of the campaign. But again, if you people reveal something to me, I'll answer it the appropriate way."

It was classic Trump: Throw something into play and then quickly deny that he'd thrown something into play:

"I refuse to call Megyn Kelly a bimbo, because that would not be politically correct. Instead I will only call her a lightweight reporter," he Tweeted back in January.

Conspiracy, paranoia and defamation: It's the repulsive triad that fuels the Trump juggernaut.

From his utterly fact-deprived charge that the ebola virus was "much easier to transmit than the CDC and government representatives are admitting," to his endless rehashing of the so-called "Obama Birther" conspiracy and his spreading of the debunked theory that childhood vaccinations cause autism, Trump has never met a scurrilous claim that he doesn't like.

Or at least, he has not found one upon which he could not cynically capitalize.

And it would be one thing if Trump were some garden variety conspiracy theorist who prowls the dark recesses of the Web, only to emerge on conservative talk radio or one of those faux-history shows that air occasionally on basic cable.

But he's not.

He is, as he continually reminds us, a Wharton-educated tycoon who could conceivably become the nation's 45th chief executive and the leader of one of the world's last, great representative democracies.

But instead of rising above such dangerous and fact-challenged muck, he gleefully rolls around in it.

For all of her clear faults - and they are many - even as flawed a candidate as Hillary Clinton can at least be credited for not trafficking in such utter nonsense.

But Trump does - and he succeeds in the doing of it - because he knows that his legion of followers, who feed on distrust of institutions, subscribe to many of the same discredited theories, and who have been taught by the Web to disregard truth even when it is staring them squarely in the face, will reward, not penalize him.

"We have never had a president whose character proved to be more admirable once he was in office than it had appeared during the campaign," Charles Murray, of The American Enterprise Institute wrote in The National Review this week. "What you see on your television screen every day from Donald Trump the candidate is the best that you can expect from Donald Trump the president."

Fortunately, it's still not too late for voters to change the channel.