When John Bel Edwards spoke at Southern University last month, a lanky young man named Joshua Standifer was among those in the audience, video camera in hand.

Standifer — known by political pros as a “tracker” — was there to film Edwards in case Edwards said something that could be used later to rough him up in the governor’s race.

He hit paydirt.

The campaign of U.S. Sen. David Vitter began using a clip of Edwards’ comments at Southern in an attack ad airing this week that ties the Democratic state representative to President Obama and accuses him of wanting to release 5,500 “thugs” from prison. The controversial ad launched as Edwards and Vitter, who will meet in a Nov. 21 runoff, began vying for the mostly conservative voters who supported either Lt. Gov. Jay Dardenne or Public Service Commissioner Scott Angelle in the primary.

Campaign trackers like Standifer are not new — in fact, they’ve become a standard feature of national political campaigns. And he’s not the only one working the Louisiana circuit: As he hounds Vitter’s opponents, a liberal outfit has sicced its own trackers onto Vitter. But Standifer has had a greater presence than any tracker before him in Louisiana, exhaustively traveling the state to film and record public appearances not only of Edwards but also of Angelle and Dardenne.

“He was everywhere we were,” said Dardenne. “I thought he must have been cloned.”

The collection of raw video footage by opposition researchers doesn’t normally attract much attention. But it has gotten more notice with the recent arrest of a private investigator hired by Vitter’s campaign, who fled on foot after Jefferson Parish Newell Normand accused him of secretly recording a conversation he and several friends were having at an Old Metairie coffee shop the day before the primary election. Normand is a long-standing and outspoken foe of Vitter.

Most campaigns and super PACs make a clear distinction between the accusation faced by Vitter gumshoe Robert Frenzel — that he surreptitiously recorded the others — and the work by Standifer, as well as a tracker working for a Democratic super PAC who films Vitter during his public appearances. Trackers make no secret of what they’re up to. In fact, they sometimes go out of their way to antagonize their targets, hoping they’ll get some juicy footage.

But tracking and stealth espionage both operate in the grainy netherworld of opposition research, a world that campaigns tend to be loath to discuss.

“We do not name our trackers in the press,” said Ben Ray, the communications director for American Bridge 21st Century, a super PAC that favors Edwards. “Their job is just to record. They are not there to talk or be part of the story. They are trained to be exceedingly polite.”

They have to keep their cool even when a powerful senator gets in their face, as happened to the American Bridge tracker in Lafayette at the Café Vermillionville Monday night. Vitter was there to attend a fundraiser.

Video posted by American Bridge shows Vitter breaking off a conversation in the restaurant lobby to pull out his cell phone and begin taking photos of the tracker.

“So I just want to clarify,” Vitter told him, “you’re recording private peoples’ conversations here?”

After the tracker acknowledged only that he was recording, Vitter accused him of “spy activity” and went to speak with a restaurant employee.

“He doesn’t want you filming,” she told the tracker as she asked him to leave. He complied without complaint.

Dardenne laughed about the video.

“He can give it out, but he can’t take it,” said Dardenne, who was repeatedly attacked in pro-Vitter TV commercials that he believes used images gathered by Standifer. (Legally, Vitter’s campaign cannot coordinate his activities with the super PAC, although it is run by a longtime member of his inner circle.)

That a candidate must not confront the tracker is a cardinal rule in the digital age. Dardenne said he thinks Vitter broke it at the restaurant because he thought he could get the tracker to admit that he was recording a private conversation, to try to minimize complaints about what his private eye had done at the coffee shop.

“This is David trying to beat them at their own game,” Dardenne said. The Vitter campaign did not respond to an email request for a comment.

In interviews Friday, Dardenne and Edwards lamented the rise of trackers as a sign of increasing incivility in modern politics.

“Everything that is said is immediately put on Facebook and Twitter,” Dardenne said. “Everything is instantaneous.”

Trackers first attracted wide national notice when Virginia Sen. George Allen, during his 2006 re-election campaign, heckled a tracker of Indian descent by calling him “macaca.” Accused of using a racist term, Allen lost momentum and then the race.

Other candidates around the country have been forced on the defensive from comments recorded by trackers.

In 2014, Bill Cassidy and Mary Landrieu had trackers at each others’ campaign events during their Senate race, eventually won by Cassidy. They also had aides hold up white-noise devices aimed at distorting the trackers’ recordings.

“Generally, trackers are someone young with thick skin,” said T. Bradley Keith, who was Landrieu’s deputy campaign manager. “It can be an unpleasant job.”

American Bridge — a national group that supports Democrats — has more than 30 trackers throughout the country, said Ben Ray, the group’s spokesman.

“It’s part of running for office, to be held accountable for what you say,” he said. Asked about complaints that the work is intrusive, Ray said, “There is nothing subtle or secretive about what we do.”

He said America Bridge doesn’t follow candidates home, “and we try to leave families out of it.”

Asked how — or whether — American Bridge’s trackers try to avoid capturing private conversations, Ray replied, in an email, “We train our trackers to roll tape any time they are working so that we can protect them from frivolous accusations, and they evaluate case-by-case how close to get to the candidate.”

Vitter clearly didn’t think the group’s tracker was coloring within the lines at the restaurant in Lafayette. And both Edwards and Dardenne feel that Standifer often fails to respect personal boundaries.

Edwards said that Standifer typically filmed him during the legislative session when he left the House chamber to talk to constituents in the hall.

“Some of the conversations were very, very private,” Edwards said. “He was very aggressive. I do believe he crosses the line.”

Edwards once told a reporter that he wanted to conduct an interview in the chamber, rather than the hall, to avoid having Standifer record it.

Cathy Dardenne, the lieutenant governor’s wife, said she found Standifer “very unnerving.”

She added, “We never felt like we had anything to hide, but you could do something in the course of the day that would look ridiculous if it was recorded.”

Standifer works for America Rising, a Republican political group based in Alexandria, Va. The pro-Vitter super PAC, the Fund for Louisiana’s Future, has paid America Rising $80,000 since February for “consulting and research services,” according to its campaign finance report. A spokesman for America Rising declined to comment.

Standifer, who filmed Edwards Friday when he received the endorsement of the Louisiana Sheriffs’ Association, has been cordial but close-mouthed on the campaign trail. He has given his name but said no more.

His LinkedIn page shows that he attended an evangelical Christian university in Tennessee, has worked for two campaigns in that state and also has a background in advertising and video production.

He told Cathy Dardenne at one campaign stop that he has a young wife and child.

“He’s hoping he’ll get a job out of this,” she said. “We had many discussions. It’s hard for us to be around people and not talk to him. Perhaps that’s naïve of us.”

Edwards limited his conversations with Standifer but said he sent food and water out to him several times when the tracker was camped for hours outside of an event.

“We have tried to treat him better than he’s treated us,” Edwards said.

Capitol bureau reporter Elizabeth Crisp contributed to this article.