WASHINGTON • Mr Joe Biden sowed doubt about the integrity of the United States presidential election by suggesting last Saturday that the only way he can lose is if there is "chicanery" at polling stations.
"Make sure you vote. Because the only way we lose this is by the chicanery going on relative to polling places," the Democratic presidential nominee told supporters in Erie, Pennsylvania.
Mr Biden later said "I'm going to accept the outcome of this election, period", and that he was referring to "attempts that are made to try to influence and scare people from voting". The line echoed US President Donald Trump's repeated efforts to question election integrity.
Mr Trump, who is trailing Mr Biden in most national and battleground state opinion polls, has suggested without evidence that mail-in ballots are subject to widespread fraud and is preparing to challenge results that do not go his way.
"The only way we're going to lose is if there's mischief," Mr Trump said last month.
Mr Biden has been urging his supporters to vote in numbers that give him a clear victory so that Mr Trump has no grounds to contest the outcome.
"The American people are voting and they're voting in large numbers," Mr Biden later told reporters, saying that his earlier remark was taken out of context. "They're going to determine the outcome and I'm going to accept the outcome of the election without any question."
But his comments also came as a warning of bad things happening at polling places - the same kind for which he has chastised Mr Trump.
Mr Biden spoke in Pennsylvania hours after a judge there rejected the Trump campaign's challenge to the state's vote-by-mail procedures.
Fraudulent messages about voting have been drawing attention as both campaigns ramp up data collection and voter targeting using their own technology to circumvent restrictions imposed by social media platforms following the Cambridge Analytica scandal.
"Your early vote has not been recorded," one text message said, with a link for more information.
Other messages tell voters they are not registered or offer unverified information on a political opponent.
Facebook barred apps that scraped data on users and their contacts after revelations about the now-defunct British consulting group Cambridge Analytica.
But in response, Mr Trump's campaign and some activist groups are using their own methods.
"What we are seeing is almost more potent than in 2016," said University of Texas Professor Samuel Woolley, who leads propaganda research at the school's Centre for Media Engagement.
Prof Woolley's team, which examined messages like those mentioned, found that the Trump mobile app, and to a lesser extent those of Mr Biden and other political activist groups, had scooped data to create profiles to craft personalised, targeted messages by SMS, e-mail or social media.
Some apps collect data not only on the users, but also their contacts, and track location and other activities such as shopping or church attendance.
Campaigns can combine that with third-party information to fine-tune messages to specific individuals or groups.
"In 2016, there was more reliance on Facebook and other social platforms, but now the campaigns have taken the collection of data into their own hands," said Prof Woolley, who called the Trump app a "surveillance tool".
Dozens of unsolicited texts, many with pro-Trump messages, surprised a 32-year-old software program manager in Boston. One read: "Looting. Rioting. Burning Cities. These are the realities of a Biden America."
"My reaction to these was initially confusion," he said. "I do not make a habit of signing up for conservative-leaning political entities."
Many message recipients have never downloaded a political app or signed up for notifications, according to researchers.
"You don't need consent to send these messages," said Mr Jacob Gursky, a researcher with Prof Woolley's team.
Some messages are effectively campaign ads, but without the disclosure required by social media platforms and other media.
The Federal Bureau of Investigation (FBI) has launched a "protected voices" project investigating potential criminal violations in such messages.
"Intentionally deceiving qualified voters to prevent them from voting is voter suppression - and it is a federal crime," the FBI said last month.
Neither the Trump nor Biden campaigns responded to requests on their data protection or privacy policies.
BLOOMBERG, AGENCE FRANCE-PRESSE