On the eve of one of the newsiest days of the 2016 presidential election season, a group of Russian operatives fired off tweets at a furious pace, about a dozen each minute. By the time they finished, more than 18,000 had been sent through cyberspace toward unwitting U.S. voters, making it the busiest day by far in a disinformation operation whose aftermath is still roiling U.S. politics.

The reason for this burst of activity on Oct. 6, 2016, documented in a new trove of 3 million Russian tweets collected by Clemson University researchers, is a mystery that has generated intriguing theories but no definitive explanation.

The theories attempt to make sense of how such a heavy flow of Russian disinformation might be related to what came immediately after, on Oct. 7.

This was the day when WikiLeaks began releasing embarrassing e-mails that Russian intelligence operatives had stolen from Hillary Clinton’s campaign chairman, revealing sensitive internal conversations that would stir controversy for weeks.

The Clemson researchers and others familiar with their findings think there likely is a connection between this looming release and the torrent of tweets, which varied widely in content but included a heavy dose of political commentary. “Hillary Clinton and Donald Trump: Which one is worse: Lucifer, Satan or The Devil?” said one tweet from an account called Gwenny, which directed readers to a YouTube video.

Complicating this analysis is the number of other noteworthy events on that day, which is best remembered for the Washington Post’s publication of the “Access Hollywood” recording of Donald Trump.

Also on that day, U.S. intelligence officials first made public their growing concerns about Russian meddling in the presidential election, following reports about the hacking of prominent Americans and intrusions into election systems in several states.

Could the Russian disinformation teams have gotten advanced notice of the WikiLeaks release, sending the operatives into overdrive to shape public reactions to the news? And what do the operatives’ actions that day reveal about Russia’s strategy and tactics now that Americans are heading into another crucial election?

These questions flow from the work of a pair of Clemson researchers who have assembled the largest trove of Russian disinformation tweets available so far. The database includes tweets between February 2014 and May 2018, all from accounts that Twitter has identified as part of the disinformation campaign waged by the Russia-based Internet Research Agency.

Collectively, the new data offer yet more evidence of the coordinated nature of Russia’s attempt to manipulate the U.S. election. The Clemson researchers dubbed it “state-sponsored agenda building.”

The tweets overall reveal a highly adaptive operation that interacted tens of millions of times with authentic Twitter users — many of whom retweeted the Russian accounts — and frequently shifted tactics in response to public events, such as Hillary Clinton’s stumble at a Sept. 11 memorial.

The researchers also found that the Russians working for the Internet Research Agency — often called “trolls” for their efforts to secretly manipulate online conversation — picked up their average pace of tweeting after Trump’s election. This was especially true for the more than 600 accounts targeting the conservative voters who were part of his electoral base, a surge the researchers suspect was an effort to shape the political agenda during the transition period by energizing core supporters.

But for sheer curiosity, nothing in the Clemson data set rivals Oct. 6. The remarkable combination of news events the following day has several analysts, including the Clemson researchers, suspect there likely was a connection to the coming WikiLeaks release. (There is no obvious evidence connecting the tweets to the release of the Trump recording, say the researchers and others familiar with their findings.)

Last week’s indictment of Russian intelligence officers by Special Counsel Robert Mueller made clear that the hack of Clinton campaign chairman John Podesta’s e-mails and their distribution through WikiLeaks was a meticulous operation. Tipping off the Internet Research Agency, the St. Petersburg troll factory owned by an associate of President Vladimir Putin, might have been part of an overarching plan of execution, said several people familiar with the Clemson findings about the activity of the Russian trolls.

“They tend to ramp up when they know something’s coming,” said Clint Watts, a former FBI agent and expert on the Russian troll armies and how they respond to news.

Though Watts did not participate in the Clemson research, his instincts fit with those of the researchers — Darren Linvill and Patrick Warren — who point to the odd consistency of the storm of tweets. More than on any other day, the trolls on Oct. 6 focused their energies on a left-leaning audience, with more than 70 percent of the tweets targeting Clinton’s natural constituency of liberals, environmentalists and blacks.

Linvill and Warren, who have written a paper on their research now undergoing peer review, identified 230 accounts they categorized as “Left Trolls” because they sought to infiltrate left-wing conversation on Twitter.

But the Left Trolls did so in a way clearly designed to damage Clinton, who is portrayed as corrupt, in poor health, dishonest and insensitive to the needs of working-class voters and minority groups. By contrast, the Left Trolls celebrated Vermont Sen. Bernie Sanders and his insurgent primary campaign against Clinton and, in the general election, Green Party candidate Jill Stein.

Less than two weeks before Election Day, for example, the Left Troll account Blacktivists tweeted, “NO LIVES MATTER TO HILLARY CLINTON. ONLY VOTES MATTER TO HILLARY CLINTON.”

Ninety-three of the Left Troll accounts were active on Oct. 6 and 7, each with an average following of 1,760 other Twitter accounts. Taken together, their messages could have directly reached Twitter accounts 20 million times on those two days, and reached millions of others through retweets, the Clemson researchers found.

The release of Podesta’s e-mails made public candid, unflattering comments about Sanders and fueled allegations that Clinton had triumphed over him because of her connections to the Democratic Party establishment.