A man who was known as a far-right Twitter troll was arrested Wednesday and charged with spreading disinformation online that tricked Democratic voters in 2016 into trying to cast their ballots by phone instead of going to the polls.

Federal prosecutors accused Douglass Mackey, 31, of coordinating with co-conspirators to spread memes on Twitter falsely claiming that Hillary Clinton’s supporters could vote by sending a text message to a specific phone number.

The co-conspirators were not named in the complaint, but one of them was Anthime Gionet, a far-right media personality known as “Baked Alaska,” who was arrested after participating in the Jan. 6 riot at the U.S. Capitol, according to a person briefed on the investigation, who spoke on the condition of anonymity to discuss an ongoing investigation.

As a result of the misinformation campaign, prosecutors said, at least 4,900 unique phone numbers texted the number in a futile effort to cast votes for Clinton.

Mackey was arrested this morning in West Palm Beach, Florida, in what appeared to be the first criminal case in the country involving voter suppression through the spread of disinformation on Twitter.

“With Mackey’s arrest, we serve notice that those who would subvert the democratic process in this manner cannot rely on the cloak of internet anonymity to evade responsibility for their crimes,” said Seth DuCharme, the acting U.S. attorney in Brooklyn, New York, whose office is prosecuting the case.

Clinton was not named in the complaint, but a person briefed on the investigation confirmed that she was the presidential candidate described in the charging documents.

A lawyer for Mackey declined to comment.

Mackey, who was released from custody Wednesday on a $50,000 bond, faces an unusual charge: conspiracy to violate rights, which makes it illegal for people to conspire to “oppress” or “intimidate” anyone from exercising a constitutional right, such as voting. The charge carries a maximum sentence of 10 years in prison.

The case will test the novel use of federal civil rights laws as a tool to hold people accountable for misinformation campaigns intended to interfere with elections, a problem that has recently become an urgent priority for social media platforms and law enforcement officials to stop.

It has become a game of whack-a-mole to police users like Mackey, who prosecutors said would simply open new Twitter accounts after his old ones were suspended. Mackey used four different Twitter accounts from 2014 to 2018, the complaint said, always seeking to hide his true identity from the public.

The goal of Mackey’s campaign, according to prosecutors, was to influence people to vote in a “legally invalid manner.”

In 2018, Mackey was revealed to be the operator of a Twitter account using the pseudonym Ricky Vaughn, which boosted former President Donald Trump while spreading anti-Semitic and white nationalist propaganda.

Mackey’s account had such a large following that it made the MIT Media Lab’s list of the top 150 influencers in the 2016 election, ranking ahead of the Twitter accounts for NBC News, Drudge Report and CBS News.

Twitter shut down the account in 2016, one month before the election, for violating the company’s rules by “participating in targeted abuse.” At that time, the account had about 58,000 followers. Three days later, an associate of Mackey’s opened a new account for him, prosecutors said, which was also quickly suspended.

It was not clear how Mackey became connected to Gionet, or “Baked Alaska,” who was also a popular social media figure among white nationalists and far-right activists. A lawyer for Gionet declined to comment.

Mackey is a Vermont native who graduated from Middlebury College. He worked for five years as an economist at a Brooklyn-based research firm, John Dunham & Associates, until his termination in the summer of 2016, a company representative said.

The complaint showed a surgical precision in the disinformation campaign by Mackey and his four co-conspirators. In private group conversations on Twitter, they discussed how to insert their memes into trending conversations online and dissected changes in wording and colors to make their messages more effective.

Mackey was obsessed with his posts going viral, the complaint said, once telling his associates, “THE MEMES ARE SPREADING.” He and his co-conspirators joked about tricking “dopey” liberals.

Their effort to misinform voters began after the group saw a similar campaign intended to deceive voters in the 2016 referendum in Britain on whether to leave the European Union, also known as Brexit, according to the complaint.

Mackey and his associates created their own version, sharing photos that urged Clinton’s supporters to vote for her on Election Day using a hashtag on Twitter or Facebook. To make the images look more legitimate, they affixed the logo of her campaign and linked to her website.

Some of their memes appeared to target Black and Latino voters. One image had a Black woman standing in front of a sign supporting Clinton, telling people to vote for Clinton by texting a specific number. Mackey shared a similar image written in Spanish, prosecutors said.

Less than a week before Election Day, the complaint said, Mackey sent a message on Twitter: “Obviously, we can win Pennsylvania. The key is to drive up turnout with non-college whites, and limit black turnout.”

Around that time, Twitter began removing the images with false information and suspended Mackey’s account. But the memes had already taken on a life of their own, prosecutors said, as his associates continued to share them with a wider audience.