The posters dotting the streets of Buenos Aires had a certain Soviet flair to them.
There was one of Argentina’s presidential candidates, Sergio Massa, dressed in a shirt with what appeared to be military medals, pointing to a blue sky. He was surrounded by hundreds of older people — in drab clothing, with serious, and often disfigured, faces — looked toward him in hope.
The style was no mistake. The illustrator had been given clear instructions.
“Sovietic Political propaganda poster illustration by Gustav Klutsis featuring a leader, masssa, standing firmly,” said a prompt that Mr. Massa’s campaign fed into an artificial-intelligence program to produce the image. “Symbols of unity and power fill the environment,” the prompt continued. “The image exudes authority and determination.”
Javier Milei, the other candidate in Sunday’s runoff election, has struck back by sharing what appear to be A.I. images depicting Mr. Massa as a Chinese communist leader and himself as a cuddly cartoon lion. They have been viewed more than 30 million times.
Argentina’s election has quickly become a testing ground for A.I. in campaigns, with the two candidates and their supporters employing the technology to doctor existing images and videos and create others from scratch.
A.I. has made candidates say things they did not, and put them in famous movies and memes. It has created campaign posters, and triggered debates over whether real videos are actually real.
A.I.’s prominent role in Argentina’s campaign and the political debate it has set off underscore the technology’s growing prevalence and show that, with its expanding power and falling cost, it is now likely to be a factor in many democratic elections around the globe.
Experts compare the moment to the early days of social media, a technology offering tantalizing new tools for politics — and unforeseen threats.
Mr. Massa’s campaign has created an A.I. system that can create images and videos of many of the election’s main players — the candidates, running mates, political allies — doing a wide variety of things.
The campaign has used A.I. to portray Mr. Massa, Argentina’s staid center-left economy minister, as strong, fearless and charismatic, including videos that show him as a soldier in war, a Ghostbuster and Indiana Jones, as well as posters that evoke Barack Obama’s 2008 “Hope” poster and a cover of The New Yorker.
The campaign has also used the system to depict his opponent, Mr. Milei — a far-right libertarian economist and television personality known for outbursts — as unstable, putting him in films like “Clockwork Orange” and “Fear and Loathing in Las Vegas.”
Much of the content has been clearly fake. But a few creations have toed the line of disinformation. The Massa campaign produced one “deepfake” video in which Mr. Milei explains how a market for human organs would work, something he has said philosophically fits in with his libertarian views.
“Imagine having kids and thinking that each is a long-term investment. Not in the traditional sense, but thinking of the economic potential of their organs,” says the manipulated image of Mr. Milei in the fabricated video, posted by the Massa campaign on its Instagram account for A.I. content, called “A.I. for the Homeland.”
The post’s caption says, “We asked an Artificial Intelligence to help Javier explain the business of selling organs and this happened.”
In an interview, Mr. Massa said he was shocked the first time he saw what A.I. could do. “I didn’t have my mind prepared for the world that I’m going to live in,” he said. “It’s a huge challenge. We’re on a horse that we have to ride but we still don’t know its tricks.”
The New York Times then showed him the deepfake his campaign created of Mr. Milei and human organs. He appeared disturbed. “I don’t agree with that use,” he said.
His spokesman later stressed that the post was in jest and clearly labeled A.I.-generated. His campaign said in a statement that its use of A.I. is to entertain and make political points, not deceive.
Researchers have long worried about the impact of A.I. on elections. The technology can deceive and confuse voters, casting doubt over what is real, adding to the disinformation that can be spread by social networks.
For years, those fears had largely been speculative because the technology to produce such fakes was too complicated, expensive and unsophisticated.
“Now we’ve seen this absolute explosion of incredibly accessible and increasingly powerful democratized tool sets, and that calculation has radically changed,” said Henry Ajder, an expert based in England who has advised governments on A.I.-generated content.
This year, a mayoral candidate in Toronto used gloomy A.I.-generated images of homeless people to telegraph what Toronto would turn into if he weren’t elected. In the United States, the Republican Party posted a video created with A.I. that shows China invading Taiwan and other dystopian scenes to depict what it says would happen if President Biden wins a second term.
And the campaign of Gov. Ron DeSantis of Florida shared a video showing A.I.-generated images of Donald J. Trump hugging Dr. Anthony S. Fauci, who has become an enemy on the American right for his role leading the nation’s pandemic response.
So far, the A.I.-generated content shared by the campaigns in Argentina has either been labeled A.I. generated or is so clearly fabricated that it is unlikely it would deceive even the most credulous voters. Instead, the technology has supercharged the ability to create viral content that previously would have taken teams of graphic designers days or weeks to complete.
Meta, the company that owns Facebook and Instagram, said this week that it would require political ads to disclose whether they used A.I. Other unpaid posts on the sites that use A.I., even if related to politics, would not be required to carry any disclosures. The U.S. Federal Election Commission is also considering whether to regulate the use of A.I. in political ads.
The Institute for Strategic Dialogue, a London-based research group that studies internet platforms, signed a letter urging such regulations. Isabelle Frances-Wright, the group’s head of technology and society, said the extensive use of A.I. in Argentina’s election was worrisome.
“I absolutely think it’s a slippery slope,” she said. “In a year from now, what already seems very realistic will only seem more so.”
The Massa campaign said it decided to use A.I. in an effort to show that Peronism, the 78-year-old political movement behind Mr. Massa, can appeal to young voters by mixing Mr. Massa’s image with pop and meme culture.
To do so, campaign engineers and artists fed photos of Argentina’s various political players into an open-source software called Stable Diffusion to train their own A.I. system so that it could create fake images of those real people. They can now quickly produce an image or video of more than a dozen top political players in Argentina doing almost anything they ask.
During the campaign, Mr. Massa’s communications team has briefed artists working with the campaign’s A.I. on which messages or emotions they want the images to impart, such as national unity, family values and fear. The artists have then brainstormed ideas to put Mr. Massa or Mr. Milei, as well as other political figures, into content that references films, memes, artistic styles or moments in history.
For Halloween, the Massa campaign told its A.I. to create a series of cartoonish images of Mr. Milei and his allies as zombies. The campaign also used A.I. to create a dramatic movie trailer, featuring Buenos Aires, Argentina’s capital, burning, Mr. Milei as an evil villain in a straitjacket and Mr. Massa as the hero who will save the country.
The A.I. images have also shown up in the real world. The Soviet posters were one of the dozens of designs that Mr. Massa’s campaign and supporters printed to post across Argentina’s public spaces.
Some images were generated by the campaign’s A.I., while others were created by supporters using A.I., including one of the most well-known, an image of Mr. Massa riding a horse in the style of José de San Martín, an Argentine independence hero.
“Massa was too stiff,” said Octavio Tome, a community organizer who helped create the image. “We’re showing a boss-like Massa, and he’s very Argentine.”
The rise of A.I. in Argentina’s election has also made some voters question what is real. After a video circulated last week of Mr. Massa looking exhausted after a campaign event, his critics accused him of being on drugs. His supporters quickly struck back, claiming the video was actually a deepfake.
His campaign confirmed, however, that the video was, in fact, real, but said that Mr. Massa was not on drugs.
Mr. Massa said people were already using A.I. to try to cover up past mistakes or scandals. “It’s very easy to hide behind artificial intelligence when something you said come out, and you didn’t want them to,” Mr. Massa said in the interview.
Earlier in the race, Patricia Bullrich, a candidate who failed to qualify for the runoff, tried to explain away leaked audio recordings of her economic adviser offering a woman a job in exchange for sex by saying the recordings were fabricated. “They can fake voices, alter videos,” she said.
Were the recordings real or fake? It’s unclear.