"She will never win," Gabriella tweeted emphatically on Monday, hours before the polls opened on Election Day. "Stealing is not winning, it's losing."

"Hillary Hillary Hillary!" Mel tweeted in the same hour, with equal enthusiasm.

As the war for hearts and minds and votes entered the final battle, it was no time for partisans to relent. Democratic candidate Hillary Clinton and her team email blasted and tweeted and canvased and threw an enormous rally and filled the airwaves with ads. Republican candidate Donald Trump and his team tweeted and threw rallies and tweeted some more. And the people? Well, they clashed on Facebook, in line at the grocery store, and on Twitter (did we mention Twitter?).

"It's 7:10 PM EST in Washington DC and Donald Trump is still a major threat to the free world," one clearly pro-Hillary Twitter user tweeted. "And he still has small hands. #DumpTrump"

"#TrumpWinsBecause the American people are too smart to fall for lies anymore," Marie retweeted someone else named Halley.

But it was on Twitter where something was afoot. You see, humans weren't the only ones fighting. Those quotes above? They were almost definitely written by bots (and in Marie and Halley's case, a bot that retweeted another bot). So much of the traffic on the social network is already generated by automated bots, and that's even truer for political topics in this crazy election season. A third of pro-Trump tweets and about a fifth of pro-Clinton tweets between the first and second debates, for instance, came from bot accounts, which produced more than 1 million tweets in total, according to research from Oxford University. Yes, not all these bots are the same: some are individual operators that try to raise awareness around important issues; others are networks that tweet the same exact thing from different accounts; still others tweet the same hashtags over and over again. (These last two qualify as spam and are likely to be taken down when reported to Twitter.)

All this bot activity could be changing your perception of the election. And that's the point. This is a propaganda war. It's being fought with hyperpartisan Facebook posts, Macedonia-run political news websites and, yes, fake Twitter bots. And today, the bots fight their most important battle yet.

How ? Election Bots ? Work

Twitter is the perfect breeding ground for bots. “The thing about the platform that makes it so irresistible for bot makers is the context-free nature of communication, as well as the restricted character count,” says K. Thor Jensen, a 40-year-old writer who has created a political bot of his own that responds to Trump’s Twitter account in under five seconds. Perfect, Jensen says, for short, declarative sentences tuned for maximum impact and reach on the social network.

Of course, that's the same thing that makes it irresistible to Donald Trump, who has a far more provocative Twitter presence than Clinton. And the numbers suggest his audience is rapt. By late September of this year, Trump passed Hillary Clinton in number of followers. His likes and retweets took off in a meteoric way. Right now, Trump has 13 million Twitter followers, compared with Hillary’s 10.2 million.

But how many of these are bots? According to Sam Woolley, a researcher from Oxford University’s Project on Computational Propaganda (which has not been peer reviewed), about 50 to 55 percent of Clinton’s Twitter activity—the likes, follows, and retweets she gets—is from bots, which is typical for high-profile public figures. But Trump’s automated Twitter activity, according to Woolley, is a much higher 80 percent.

The content these bots generate is enormous. In the last debate alone, bots accounted for nearly 25 percent of debate-related tweets, the Project on Computational Propaganda found. Roughly one in four debate tweets was from a bot. And pro-Trump activity has only intensified as the election campaign has gone on. By the third debate, bots posting pro-Trump tweets outnumbered pro-Clinton bot tweets 7 to 1.

“Never have we seen such an all-out bot war,” wrote Woolley. Twitter, meanwhile, takes issue with the methods used in Oxford University's research, saying the parameters they set to detect bots aren't good enough. But Katherine Ognyanova, an assistant professor of communication at Rutgers University, agrees that bots have had an effect on the election. “[The bots'] strongest effects go through the media coverage it gets, which reaches a broad audience,” says Ognyanova. She points to the harms of TV networks and other news outlets reporting Twitter statistics that may be skewed by bot activity. Others, she worries, quote bot tweets as though they were real. Woolley hypothesizes that the worst result of such spread of "misinformation or propaganda" is that is creates "bandwagon effects around specific candidates, or acts as a mouthpiece for marginal views of very few people that then allow other people to speak the same racist or xenophobic views.”

There’s virtually no way to figure out who creates these bots, says Philip Howard, another of the Oxford University bot researchers. That’s the whole point of bots—the actors responsible want to spread a message broadly, but don’t want that message to be traceable to an identifiable source. “There’s some evidence that the political action groups are behind some of the bots—we know that they spend money in the direction of the candidates they’re supporting,” says Howard. “But Twitter bots are also unique in that it’s possible for pretty average users to generate them.” Content and advertising shops have long used bots, Howard says, and there are many vendors that sell them cheaply by the thousands to any buyer who wants to set them loose. And this is all legit because currently, there are no rules for bot activity overseen by the Federal Elections Commission, or any other government agency.

I’m a garbage programmer, but…it took about six hours all told. K. Thor Jensen

Jensen, meanwhile, says the process of programming a bot from scratch was not difficult. “I’m a garbage programmer, but…it took about six hours all told,” he says. And once it’s all set up, there’s basically nothing else you need to do. “Mine just needs to be running in a Web browser. The better ones run on a server instance and need literally no upkeep,” Jensen says.

'Heat-Seeking Missiles'

Today is the big day for the bots. Not only is it their last chance to have the presumed desired effect of their creators—to get people to support their programmed candidate—it'll likely also be the biggest day on Twitter for discussing their favorite topics. And they can't help but flock when the topics are hot. “One of the ways that bots operate is by a heat-seeking mechanism to find out what the big hot topics are,” says Woolley. “Bots will congregate around the election.”

And the bots will be ruthless. That's their way. “It’s negative messages—things that are angry, if not hate speech, or sexist or racist,” says Howard. “Those tend to travel further, especially over bot networks.” Misinformation is rampant too, he says. Just look at instances like the scam saying you could vote for Hillary by text—clear voter disenfranchisement spread widely on Twitter, in large part using bots. Even after Twitter banned those images, they kept popping back up under new accounts. Relentless and hard to control.

Worse, though today the bots will brawl, Jensen doesn’t expect it to end here. “We won’t see the end of Twitter bot interactions by a long shot, unless we also see the end of Twitter,” he says. And after the election, Howard says, these bots could be easily repurposed for another mission—say, an impeachment campaign.

The Insidious Psychology of ? Election Bots ?

Whether the bots are battling for any good reason is less than clear. There's very little research into whether they actually sway human opinions. What experts suggest their biggest effect may be is making people feel comfortable expressing opinions they already hold if they previously worried they were taboo.

“It’s plausible that if a citizen were to perceive a particular opinion to be more popular than they would have thought otherwise, they would be more likely to express that opinion online,” says Elliot Panek, a University of Alabama professor who studies the psychological effects of new media. “It’s pretty well-established that people’s behavior and likeliness of expressing opinions is in part based on what they perceive to be acceptable within a culture.” Social media and viral content, he says, is particularly good at making people believe there's momentum behind an idea or philosophy, even when much of it is artificial.

And that’s the rather insidious danger that Twitter bots can create. As Woolley points out, there’s a perceived infallibility to statistics, science and numbers. What if you can manufacture that to tell a different story? “Bots can be used to push numbers in support of a campaign—like the Trump campaign—to say they’re winning the online polls,” he says, “and to make the mainstream media polls, which are using viable, tested methods for statistical analysis and having representative samples, look like they’re manipulated.” Ognyanova agrees, saying such a narrative provides a pretext for the Trump campaign to claim the people are behind Trump. As Woolley puts it: “Bots are just a tool for making the numbers look how you want them to look.”

The thing is, when it comes to actually tallying the numbers, well, bots can't vote.

Update on 11/08/16 10AM ET: Updated with comment from Twitter.