The problem is, Pepe, Francisco, and Alberto aren't people. They're bots—spam accounts that post autonomously using programmed scripts.

Trump's rhetoric has alienated much of the Latino electorate, a fast-growing voting community. And while it's unclear who's behind the accounts of Pepe and his digital pals, their tweets succeed in impersonating Latino voters at a time when the real estate mogul needs them most.

If bots can spread lies about your rivals, why not unleash them?

Bots tend to have few followers and disappear quickly, dropping propaganda bombs as they go. Or they just sit around and do nothing. According to the site TwitterAudit, one in four of Trump's followers is fake, and similar ratios run through the accounts of the other presidential hopefuls. Even if most of these bots are inactive, they still exaggerate a candidate's popularity. Our team of researchers at the University of Washington and the University of Oxford tracks bot activity in politics all over the world, and what we see is disturbing. In past elections, politicians, government agencies, and advocacy groups have used bots to engage voters and spread messages. We've caught bots disseminating lies, attacking people, and poisoning conversations.