Donald Trump's Twitter followers have earned an oft-deserved bad rap for their unsavory online antics. They've purportedly doxed student activists, launched a series of anti-Semitic attacks against Jewish authors and journalists, and were just this week implicated in a campaign of harassment against the actress Leslie Jones.

But even as repugnant as Trump Twitter can get, Trump Reddit looks far worse. That's according to an investigation we carried out over the past few days, which found that the moderators of some of Trump's Reddit fan clubs rub elbows with neo-Nazis and white supremacists, among others.

"The overwhelming majority of Trump supporters do not sympathize with Neo-Nazis or virulent racism," said r/teh_donald, who moderates r/the_donald, Reddit's second-largest and most active pro-Trump subreddit. Still, he admits, that element does exist: Earlier this month, r/the_donald dismissed one of its own moderators for plotting a pro-Trump white supremacist subreddit.

Among social networks, Reddit is unique for a variety of reasons. For one thing, it has historically been a free-for-all: The "government of a new type of community," per former CEO Yishan Wong, where "every man is responsible for his own soul" and where even the most vile or hateful communities could flourish without fear of removal. (The Southern Poverty Law Center once ruled it a "black hole" and the home of the "most violently racist Internet content.") For another thing, users don't belong to one massive pool, a la Twitter. Instead, they self-organize into smaller affinity communities, called subreddits, which are controlled by user volunteers.

By mapping these affinity groups according to the people who run them, it's possible to nail down which groups share moderators in common. It also suggests the degree to which certain affinities or interests overlap: For instance, the group r/thedangerousfa**ot, a fan club for gay Breitbart tech reporter Milo Yiannopoulos, shares two mods in common with r/rightwingLGBT. So there is a clear overlap there, at least to a certain degree.

When it comes to the Trump universe — which we began mapping from the largest groups, and spiralled out from there — many of those overlaps are precisely what you'd expect. Several moderators of r/the_donald are also involved in groups aligned with the "alt-right," an insurgent and uniquely Internet-y strain of conservatism. And several mods who are big on Trump Reddit also oversee pages like r/the_farage, r/Danish and r/European, which are devoted to Europe's nationalist movement.

But there are more unsettling affinities, as well. The largest Trump group on Reddit, with 276,000 subscribers, is r/DonaldTrump2016. One of the moderators of that group also oversees r/Quranimals, which self-identifies as an anti-Muslim "hate sub," and r/Rapefugees, which is virulently anti-migration. Other mods of the group are involved with r/eugenics and r/betauprising (which advocates a society in which women cannot "choose with whom they want to have sex.") Another mod, r/RamblinRambo3 — who also works with r/PURE_TRUMP — also moderates groups devoted to decrying Islam as a "violent and oppressive ideology," as well as a group devoted to "far right, possibly illegal memes."

As Trump subreddits go, r/PURE_TRUMP, with its 600 subscribers, isn't particularly large. But all of its mods have unsavory affiliations. For starters, there is enormous overlap between the moderators of r/PURE_TRUMP and those who oversee a cluster of "public watch" clubs, which basically exist to slur liberals, Black Lives Matter activists and members of the LGBT community in extravagantly offensive terms.

On top of that, three of r/PURE_TRUMP moderators are also involved with r/ArbeitMachtFrei, whose politics should be fairly obvious from its name. ("Arbeit Macht Frei" is the German phrase that appeared on Auschwitz's gates.) Three oversee r/ShoahThoughts, a forum for "Antisemitic/Anti-Zionist jokes." Two are involved in r/f*gworldproblems, which has been quarantined by Reddit for its "highly offensive" attacks on gay people. One r/PURE_TRUMP moderator, u/Haizenberg, is involved in five separate groups that mock Jews or invoke Hitler or the Holocaust.

To be clear, the Trump campaign has no official presence on Reddit, and it's impossible for any candidate to control the online behaviour of its fans. Trump isn't even the only candidate to face these sorts of problems: Earlier this year, the Bernie Sanders campaign scrambled to deal with overt sexism and gender-based harassment by some of its online followers. But while staffers from that campaign locked down the Sanders subreddit, apologized to victims and denounced the behaviour, the Trump campaign has taken a different approach.

"They have not done a good job distancing themselves from this," said Patrick Ruffini, a digital strategist for Republican campaigns. "Whenever one of these issues bubbles up, (the Trump campaign) sends the signal that they're OK with this activity happening on their behalf, as long as it happens on their behalf. They haven't come out strongly and denounced it."

"There's kind of this wink-wink, nod-nod to white supremacists," Ruffini added. "And so they keep doing it."

Ruffini is hopeful the campaign will change tack as more attention is drawn to it. Already, he said, the national outrage over Trump's posting of a "Star of David" meme from 4chan suggests that the public has become more sensitive to the far-right proclivities of some in Trump's audience. Tuesday night, Twitter also permanently banned the account of the aforementioned Yiannaopolous, an outspoken Trump supporter, reportedly in connection with harassment of Jones. And r/the_donald continues to crackdown on bad behaviour.

"This is about doing what is best for Donald Trump," teh_donald wrote in his June 21 post disavowing white nationalist activity in the sub. " ... They are people that Trump would want nothing to do with. Just as Trump would, we disavow them."