As Joseph R. Biden Jr. announced that he had selected Kamala Harris of California as his vice-presidential running mate, internet trolls got to work.
Since then, false and misleading information about Ms. Harris has spiked online and on TV. The activity has jumped from two dozen mentions per hour during a recent week to over 3,200 per hour in the last few days, according to the media insights company Zignal Labs, which analyzed global television broadcasts and social media.
Much of that rise is fueled by fervent supporters of President Trump and adherents of the extremist conspiracy movement QAnon, as well as by the far left, according to a New York Times analysis of the most widespread falsehoods about Ms. Harris. On Thursday, Mr. Trump himself encouraged one of the most persistent falsehoods, a racist conspiracy theory that Ms. Harris is not eligible for the vice presidency or presidency because her parents were immigrants.
“Sadly, this wave of misinformation was predictable and inevitable,” said Melissa Ryan, chief executive of Card Strategies, a consulting firm that researches disinformation.
Many of the narratives are inaccurate accusations that first surged last year during Ms. Harris’s campaign to become the Democratic presidential nominee.