Photo

Campaign rallies are crawling with hidden cameras these days as opposition researchers from rivals, activist groups or political action committees spare no expense in hopes of finding a gaffe or, ideally, signs of unlawfulness.

Presidential campaigns were put on notice on Tuesday that the stakes will be higher in this election cycle as Project Veritas Action, a research team that uses undercover investigators, warned that it was stepping up its stalking.

The group, which considers itself a journalism organization, is led by James O’Keefe, who has experienced his own legal problems over the years for lying to gain access to information. In 2010, Mr. O’Keefe pleaded guilty to misdemeanor charges and was fined for posing as a repairman to gain access to the office of former Senator Mary Landrieu of Louisiana. Two years ago, Mr. O’Keefe paid $100,000 to settle a lawsuit filed by a former Acorn member after he posed as a pimp during an investigation of the activist group.

Mr. O’Keefe’s team — which he billed as an investigative SEAL Team Six — fired an opening salvo on Tuesday by calling a news conference at the National Press Club in Washington to reveal a purported violation of campaign finance laws by Hillary Rodham Clinton’s staff members.

In a five-minute video compilation, Veritas showed senior members of Mrs. Clinton’s team appearing to accept a donation from a Canadian women at Mrs. Clinton’s campaign announcement rally in exchange for hats and pins bearing the candidate’s name. The staff members — Molly Barker and Erin Tibe — express awareness that they cannot accept a donation from a foreigner but agree to allow the Canadian woman to give the money to an American citizen standing next to her who made the transaction on her behalf.

Although the American happened to be one of Project Veritas’s staff members who used a fake name, Mr. O’Keefe made the case that the video showed a willingness by the campaign to skirt laws that forbid taking donations from foreigners by using a conduit. The transaction amounted to $75, and Project Veritas has asked Mrs. Clinton’s campaign to refund the money.

“They have demonstrated a willingness to contravene the law,” Mr. O’Keefe said.

Foreign donations are a sensitive subject for the Clintons, as their family foundation has been under scrutiny for accepting money from overseas while Mrs. Clinton was secretary of state, and recent State Department emails showed that former President Bill Clinton tried to get permission to give paid speeches in North Korea and the Democratic Republic of Congo.

On Tuesday, Mrs. Clinton’s campaign denied any wrongdoing and accused Project Veritas of attempted entrapment.

“Our staffers understand and follow the law, as demonstrated even in their selectively edited video,” said Jesse Ferguson, a campaign spokesman. “Project Veritas, on the other hand, has been caught trying to commit fraud, falsify identities and break campaign finance law — not surprising, given that their founder has already been convicted for efforts like this.”

The Federal Election Commission would not comment specifically on the case but noted that at least four commissioners would have to agree that there was a violation before any penalties could be imposed.

Christian Hilland, an F.E.C. spokesman, did point to the agency’s rules against accepting foreign money that specifies: “Federal law prohibits contributions, donations, expenditures and disbursements solicited, directed, received or made directly or indirectly by or from foreign nationals in connection with any election.”

While Mrs. Clinton’s campaign denied breaking any laws, Mr. O’Keefe and his lawyer, Benjamin Barr, acknowledged that Project Veritas did act illegally by facilitating such a donation but that the infraction on their part was so minor that it was akin to jaywalking.

Although campaign finance violations are a serious issue, Mr. O’Keefe’s presentation drew some snickers from the reporters that Project Veritas had convened for the event. He struggled to justify breaking laws and using fake names to find wrongdoing, and at one point Mr. O’Keefe was asked pointedly, “Is this a joke?”

Brushing the question off as ridicule, Mr. O’Keefe maintained that the organization was acting for the greater good to shine a light on corruption in politics and that more videos would be trickling out from its team of investigators who are spread across the country and infiltrating campaigns. Claiming not to be partisan, he said that Republican candidates should be ready, too.

“We are going to create an army of exposers,” Mr. O’Keefe said. “We’ve got more.”