For Democrats, Donald Trump’s decision to put Breitbart News chief Steve Bannon — a man they dismiss as a conspiracy theorist — in charge of his campaign is vindication of a conspiracy theory of their own.

“The merging of the vast right-wing conspiracy and the train wreck that is Trump is now complete,” said Tracy Sefl, who was the Clinton campaign’s designated “Drudge whisperer” in 2008, thanks to her unique relationship with Matt Drudge.

The Clintons have long maintained that a “vast right-wing conspiracy” is out to get them, as Hillary Clinton told NBC News’ Matt Lauer not long after The Drudge Report introduced the world to Monica Lewinsky in 1998.

They say conservative media outlets, and the donors and political operatives behind them, are responsible for creating what Bill Clinton called a “cartoon” version of his wife: A corrupt, venal, bloodstained — and now sickly — strawman that bares little resemblance to reality.

Earlier this year in New Hampshire, Hillary Clinton said the “vast right-wing conspiracy” was alive and well, adding: "At this point it's probably not correct to say it's a conspiracy because it's out in the open.”

Little did she know that eight months later, her Republican opponent would put in charge of his campaign the man who “runs the new vast right-wing conspiracy,” as Bloomberg’s Joshua Green wrote last year in a definitive profile of Bannon.

Few have done more than Bannon to help draw the 2016’s version of the Clinton “cartoon,” so the move is widely seen as a sign Trump will devote the remainder of his campaign to lurid rumors and scandalous accusations about Bill Clinton’s sex life and Hillary Clinton’s health.

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But it also suggests that Trump, who just a few years ago called the Clintons “wonderful people,” is likely to fail for the same reason the vast right-wing conspiracy of the 1990s did — buying too much into their own caricature of the Clintons and assuming the rest of America sees the same thing they do.

Bannon has actually made it his explicit goal to succeed where his predecessors failed. “In the 1990s,” he told Bloomberg, “conservative media couldn’t take down [Bill] Clinton because most of what they produced was punditry and opinion, and they always oversold the conclusion: ‘It’s clearly impeachable!’ So they wound up talking to themselves in an echo chamber.”

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So in addition to feeding that echo chamber at Breitbart — which one former staffer says has turned into "Trump’s personal Pravda" — Bannon founded the Government Accountability Institute, which digs up fact-based scoops that it shares with mainstream media outlets like the New York Times.

Bannon, for instance, helped orchestrate the publication of “Clinton Cash,” the explosive book by GAI President Peter Schweizer, which detailed alleged conflicts of interest and pay-for-play politics between the Clintons and the donors to their foundation.

While the book succeeded wildly in breaking through to the mainstream it did not mortally wound Clinton.

David Brock, who betrayed the 1990s right-wing conspiracy to found Democratic groups that now monitor the right, said he was amazed by the success Brannon and his compatriots have had in taking over the GOP — but suspects their conquest will stop there.

"The takeover of the Republican presidential campaign by the purveyor of a lunatic right-wing website may be the final chapter in the collapse of the Republican Party,” he said. “To see the lunatics actually running the asylum is another surprise in a surprising year.”

Anti-Clinton pseudo-scandals and conspiracy theories “may attract a hard right media niche audience,” Brock said, “but will repel most of the electorate in a national campaign.”

That’s a view shared by Clinton’s brain trust. On a conference call with reporters about Bannon’s hire, Clinton campaign manager Robby Mook used the term “conspiracy theory” more than dozen times and said the hire was a sign Trump would double down on his worst instincts.

Trump has well established credulity for the kind of outlandish, but worldview-confirming tales that bubble up from the fever swamps of the Internet, like claiming President Obama was born in Kenya and saying Ted Cruz’ father was involved in the JFK assassination.

Trump has long kept in touch with Roger Stone, a prolific progenitor of fringe-right conspiracy theories who writes regularly for Breitbart, though he’s kept Stone outside the official campaign.

Now Trump has brought the swamp into Trump Tower, and his campaign emails could start to look increasingly like the chain emails from which he sometimes seems to get his facts.

Lately, Breitbart and other conservative outlets have been focused on unsubstantiated claims about Hillary Clinton’s health. Trump himself indicated his interest in the subject this week, saying in prepared remarks that Clinton lacks the “mental and physical stamina” to fight terrorism.

Fox News’ Sean Hannity has been the most prominent champion of a claim that Clinton suffered a seizure in front of reporters (she did not). The Drudge Report used old photos of Clinton tripping on a flight of stairs to suggest she needs help walking (she does not). Fringier outlets have suggested Clinton faked her medical records (she did not) or that she wears a defibrillator (she does not) or that her body guard is secretly a doctor who carries anti-seizure medicine (also not true).

Clinton’s campaign, which has assiduously avoided weighing on this kind of thing, may have to spend more time pushing back. Tuesday night, the campaigns sent out a lengthy statement dismissing health rumors produced by a “well-oiled network of conspiracy peddlers.”

Clinton, like other presidential candidates, has released a letter from her longtime doctor explaining her medical history and calling her “healthy.” (Meanwhile, journalists have raised their own questions about Trump’s doctor letter, which claims he “will be the healthiest president in the history of the United States.”)

It’s possible questions about Clinton’s health will resonate in a way, say, Benghazi never did. But it seems more likely the narrative will stay trapped in the echo chamber.

Conspiracy theories are a factor in almost every campaign, from rumors that John McCain was brainwashed in Vietnam to false stories that Sarah Palin faked a pregnancy.

“But this year really does feel unusual,” said Jesse Walker, the author of “The United States of Paranoia,” an examination conspiracy theories in American history. “It's not every cycle that you basically have two campaigns essentially accusing each other of being arms of foreign powers. And Trump is shameless in a way that most major-party nominees are not — he doesn't care if what he's saying sounds disreputable, or if he's citing a source like the National Enquirer that most political players think is a joke.”

“This year a lot of stuff that would bubble beneath the surface in an ordinary campaign is bubbling right out of the candidate's mouth,” Walker added.