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A video sent to voters falsely claimed that Joe Biden wants to give “sex changes to second-graders.”

A menacing directive advised Democrats to vote for Trump “or else.”

And a years-old photograph newly circulated with erroneous instructions for how to blow past a purported poll watcher on Election Day.

These deceptive, 11th-hour messages are not finding their way to Americans via the now well-trodden paths of Facebook and Twitter. Instead, they’re arriving in waves of text messages and emails, making use of a more intimate and less heavily scrutinized vector of disinformation than the social networking services manipulated four years ago as part of the Kremlin’s sweeping interference in the 2016 election.

Texts and emails “have the potential to be more believable than social media,” said Darren Linvill, a specialist in social media at Clemson University who has studied millions of tweets sent by the Kremlin-linked Internet Research Agency. “I think people are more ready to accept information that comes through their phone than social media, where we’re trained in many ways to be more on guard.”

Each of the suspicious campaigns revealed this month targeted battleground states — from knife-edge Pennsylvania to Florida, a must-win for President Trump, and Texas, a potential pickup for Democrats. The efforts together highlight the myriad and fast-evolving methods available to both foreign and domestic actors seeking to shift votes or simply sow chaos in the final days of the presidential race.

In Pennsylvania, for example, some Democrats were startled to see their phones buzzing in recent days with an urgent message from a “Democratic volunteer with APP PAC,” little-recognized shorthand for the political action committee associated with the American Principles Project.

The conservative think tank, founded in 2009, has opposed same-sex marriage, abortion and transgender rights. The group’s executive director, Terry Schilling, said in an interview he envisions the APP as “the NRA but for families,” comparing his group to the National Rifle Association.

The text message misconstrued comments from Biden at a recent town hall, where he condemned discrimination against transgender children, to suggest he had “endorsed giving 8 and 10 year olds sex change treatments.” It included a misleading video leveling the same claim, debunked last week by the Associated Press.

Schilling defended the claim, saying Biden’s recent vow that there should be “zero discrimination” against transgender children “implied . . . that children should have a right to live as the gender they identify with, even if opposite from their biological sex, and have access to any medical treatments that will facilitate this.”

He said the PAC’s aim is to reach a million Democrats and independents in the state. RoboKiller, a company that offers a robocall and text blocking app, estimated 300,000 of the PAC’s messages had been sent on Sunday and Monday, also targeting Virginia and New Jersey, though about 90 percent of the texts went to Pennsylvania.

Schilling did not respond to a question about how the PAC had obtained contact information for Democrats in Pennsylvania. Cellphone numbers are among the data included in many commercially available voter files.

Asked about the claim in the script that the message was coming from a “Democratic volunteer,” he said the organization counts among its supporters numerous former Democrats, though he said he could not find any willing to discuss their views in an interview.

Pennsylvania’s attorney general, Democrat Josh Shapiro, said the texts should serve as a warning sign that the state, which both campaigns see as pivotal, is a “target for disinformation campaigns.”

“People must be vigilant in the coming days and analyze information they are receiving from unknown or untrusted sources,” he said.

Beyond Pennsylvania, the recent string of suspicious email and text campaigns — in addition to old-fashioned robocalls — reflects the ever-mutating challenge that government officials, election watchdogs and average voters face as they seek to separate fact from fiction during a dizzying and divisive campaign.

Candidates from both parties, following consumer trends, have invested heavily in texting technologies this cycle, benefiting from ambiguities in anti-robocall regulations affirmed in June by the Federal Communications Commission following lobbying by industry groups. Some experts warned of haziness even in understanding the potential reach of such campaigns, given barriers to tracking en masse who is sending and receiving direct messages.

“It is definitely a vector for disinformation and disenfranchisement, and unfortunately it’s going to be happening in an environment of lots of other [activity],” said Ian Vandewalker, a senior counsel for the democracy program at the Brennan Center for Justice. In addition to more visible sources of misinformation, including the “president’s Twitter feed” and prominent pages on Facebook, email and text operations represent another “piece of the puzzle, and it’s hard to say what, if anything, is going to affect a substantial number of voters.”

The potential risks became apparent last week in Florida. A flood of emails arrived in the inboxes of Democrats there, as well as in several other places, threatening to “come after” anyone who did not vote for Trump. The messages claimed to be from the far-right Proud Boys but instead were the product of a deceptive operation that the U.S. government swiftly blamed on Iran.

Earlier this month, the FBI’s field office in El Paso issued an advisory warning about an image from 2016 “being circulated through text message and social media” that conveyed misleading instructions for reporting poll watchers policing the vote. Contrary to claims in the text message, the image had not been sent out by the FBI. Nor did it contain the correct phone number for alerting federal authorities about voting irregularities.

The motive for a similarly suspect communication in Oklahoma was even less clear. The secretary of the Oklahoma State Election Board issued a notice last week after a text message wrongly warned of a polling place’s relocation and provided a phone number allegedly belonging to a male escort service.

“Voters should be very cautious about phone calls, emails, social media posts and text messages containing false information about elections,” said the election secretary, Republican Paul Ziriax. He did not indicate who was behind the message.

In other cases, officials have identified alleged culprits. At the beginning of the month, Michigan’s attorney general, Democrat Dana Nessel, filed charges against Jacob Wohl and an associate known for seeking to stage political scandals, accusing the two men of orchestrating a series of robocalls designed to suppress the vote. Wohl, 22, and his associate on Tuesday were also indicted in Ohio’s Cuyahoga County.

A message sent to an email associated with Wohl yielded no response. A lawyer representing him in Michigan, William Amadeo, said the robocalls were “protected speech.”

Estimated to include about 85,000 calls, the campaign also reached voters in urban areas in Pennsylvania, New York, Ohio and Illinois, according to prosecutors. It included baseless warnings about privacy incursions stemming from voting by mail, according to the charges in Michigan and a separate complaint brought by the National Coalition on Black Civic Participation and several individual plaintiffs in U.S. District Court for the Southern District of New York.

“Don’t be finessed into giving your private information to the man, stay home safe and beware of vote by mail,” the call advised, according to a transcript included in the New York complaint.

Such campaigns also illustrate the range of responses that cunning campaign-related communications now evoke, after years of warnings from government agencies, major technology companies and members of civil society about online deceit. Some recipients said they were prepared for trickery, all too familiar by now with the threat of foreign interference.

“I skimmed it and noticed it said Joe Biden was too extreme and assumed it was a Russian bot,” said Erik J. Brown, an author of young adult novels in Philadelphia. Brown, 33, was one of numerous Pennsylvania Democrats who on Sunday reported receiving the misleading text message about Biden from the American Principles Project’s PAC.

In Pennsylvania, the group turned to text “because it’s the most direct way to get this message to voters in such a short time frame,” said Schilling, the organization’s leader. He cited the group’s own polling in 10 swing states, which he said showed that majorities in both parties opposed hormone treatments and puberty blockers for minors. “The Democratic Party has really embraced the full spectrum of the transgender issue,” he said, defending the PAC’s messaging.

To distribute the texts, Schilling and his team used RumbleUp, a peer-to-peer texting platform. With little more than a smartphone, a decentralized corps of volunteers working at the behest of a candidate or cause can blitz existing and prospective voters with fundraising pleas and other messages.

The technology has been put to use in recent years to help Democratic and Republican candidates alike send messages to voters en masse, contributing to a new groundswell in political texts. RoboKiller estimated that a total of 2.7 billion political texts were sent in September alone.

Typically, federal law requires political campaigns and other organizations to obtain a person’s consent before sending automated messages. Carriers including AT&T, Verizon and T-Mobile, meanwhile, have in place policies and tools to block these and other unwanted spam texts, particularly if they see malicious actors sending them en masse, triggering widespread customer complaints.

But peer-to-peer texting companies contend their tools are not automated, meaning they are not as clearly covered by the government’s anti-robocall rules. A wide array of these firms and other political actors, including the Republican National Committee, successfully lobbied the U.S. government against ratcheting up regulation of the technology earlier this year, according to federal disclosures.

The gap in federal law may have allowed Schilling — and the scores of other campaigns relying on such tools — to avoid having to ask for a voter’s permission before sending the texts. Many recipients this week said they never consented to receiving such messages. The owner of RumbleUp, Thomas Peters, did not respond to a request for comment.

For email campaigns, the rules are similarly pliant. And the sender’s true identity is even easier to conceal.

So when Leslie Gilliland, a retiree in northeast Florida, received an email last week claiming to be from the Proud Boys, she took it at face value, never expecting it could be the work of a foreign nation-state.

“We were alarmed because we knew about the Proud Boys,” she said. “We took it very seriously — we contacted the sheriff’s department, and my husband called and emailed the FBI. It’s not every day you receive something like that.”