The researchers analyzed 20 million tweets generated between September 16 and October 21.
Software robots generated a significant number of Twitter messages in support of Donald Trump, distorting the Republican presidential nominee's backing on the social network, a study showed Monday.
The study by University of Southern California computer scientists found that both Trump and Democrat Hillary Clinton had supporting messages from "bots" but that Trump had more bots and produced more tweets.
"This generates a stream of support that is at staggering odds with respect to the overall negative tone that characterizes the 2016 presidential election campaigns," researchers Alessandro Bessi and Emilio Ferrara wrote in the online journal First Monday's November 7 edition.
"The fact that bots produce systematically more positive content in support of a candidate can bias the perception of the individuals exposed to it, suggesting that there exists an organic, grassroots support for a given candidate, while in reality it's all artificially generated."
The researchers analyzed 20 million tweets generated between September 16 and October 21 by about 2.8 million distinct users, and estimated that over 400,000 accounts "are likely bots."
The bots represented nearly 15 percent of the accounts while generating 3.8 million tweets of nearly 19 percent of the total conversation.
Trump's robot-produced tweets were almost uniformly positive, while only half of Clinton's were, with the other half criticizing the nominee, according to the research paper.
Using automatically-generated tweets and messages can distort "trending" topics on Twitter, and give Trump and his supporters the ability to claim, for example, that he won the presidential debates.
"Our findings suggest that the presence of social media bots can indeed negatively affect democratic political discussion rather than improving it, which in turn can potentially alter public opinion and endanger the integrity of the presidential election," the researchers said.
A similar study released last month by researchers from Oxford University, the University of Washington and Corvinus University of Budapest reached similar conclusions, finding that the pro-Trump accounts out-produced pro-Clinton accounts by seven-to-one.