Paying agitators to bait Trump supporters may be sleazy, but it’s unlikely to result in legal trouble for the Democratic operatives caught in the Project Veritas Action sting.

What may land Democrats in hot water are a number of less-noticed conversations on the explosive undercover videos released last week suggesting coordination among the Hillary Clinton campaign, the Democratic National Committee and pro-Democrat third-party groups.

At least two complaints have been filed with the Federal Election Commission requesting an investigation into suspected wrongdoing.

Such complaints face a high bar: Even when coordination is suspected, it’s difficult to find evidence showing that political campaigns worked in cahoots with third parties such as super PACs. The FEC’s three-prong test holds that complainants must show that coordination involved payment, content and conduct.

“To a large extent, the FEC has never really been forced to come down on people about this coordination,” said Joseph Vanderhulst, legal counsel for the Public Interest Legal Foundation, which filed an FEC complaint last week.

That is one reason the Project Veritas investigation is gaining attention from advocates for clean campaigning, said J. Christian Adams, the legal foundation’s president and general counsel.

“It’s hard to prove — until you start getting videos,” said Mr. Adams. “That’s what makes this so special.”

The foundation’s complaint was followed by one from Project Veritas Action, which asked the commission to act within 120 days on suspected violations of the Federal Election Campaign Act.

“This criminal conspiracy involves the knowing and willing creation of coordinated expenditures from prohibited corporate sources,” said the Project Veritas complaint filed by Benjamin Barr, who previously served as counsel to two FEC chairmen.

Transcripts from the Project Veritas investigation, titled “Rigging the Election,” show that “the supposedly independent speech and actions of third-party groups were directed, controlled, or puppeteered by [Hillary for America] or the DNC,” said the complaint.

“Indeed, the record established not just simple violations of the FECA’s coordination provisions, but ongoing knowing and willful evasion of federal election law requirements through a complicated scheme,” Mr. Barr said.

The footage shows Scott Foval, national field director of Americans United for Change, discussing his work coordinating protests against Republican presidential candidate Donald Trump with the DNC, the Clinton campaign and third-party groups.

“We have a clip deliverable that we have to deliver every day for our group of clients who are involved in this project,” Mr. Foval said in footage from Sept. 23. He then cites Americans United for Change, Alliance for Change, and the Alliance for Retired Americans, an arm of the AFL-CIO.

“And then there’s the DNC and the campaigns and Priorities. Priorities are a big part of this, too,” said Mr. Foval, apparently referring to the super PAC Priorities USA.

Priorities USA and other super PACs are barred from coordinating with candidates in part because they may accept unlimited contributions from corporations and unions, while political campaigns cannot.

“Super PACs are allowed to coordinate with one another. Where the coordination comes in is between the campaign or campaign’s agent and the super PAC,” said Brendan Fischer, Campaign Legal Center associate counsel. “So if the campaign asks the super PAC to do something, if the campaign says, ‘I want you to do this ad,’ and the super PAC does it, then that would be coordination.”

At one point, Mr. Foval indicated that he acted as an intermediary between the super PACs and the campaign. “We’re consultants, so we’re not the official entity, and so those conversations can be had between consults who are working for different parts.”

“The campaigns and DNC cannot go near Priorities, but I guarantee-damn-tee you that the people who run the super PACs all talk to each other, and we and a few other people are the hubs of that communication,” said Mr. Foval.

The Clinton campaign, the DNC and the third parties mentioned in the videos have not commented publicly on the complaints, although Mrs. Clinton said Thursday that she was unaware of the dirty tricks. “I know nothing about this,” she said.

Mr. Foval was fired shortly after the first video was released a week ago. A day later, Democracy Partners’ Robert Creamer, also featured in the video, stepped down from the presidential race.

Mr. Creamer said in his Tuesday statement that his consulting group had “always adhered to the highest standards of transparency and legality in our work for DNC.”

Mr. Vanderhulst said those named in the complaint may argue that firewalls were put into place to prevent coordination, and indeed, Mr. Foval said in the video that he had erected a “double blind” between his operation and the DNC and Clinton campaign.

“The thing we have to watch is to make sure there’s a double blind between the actual campaign and the actual DNC and what we’re doing,” Mr. Foval said. “There’s a double blind there. So they can plausibly deny that they knew anything about it.”

The Public Interest Legal Foundation complaint also calls on the FEC to investigate whether the Clinton campaign or DNC violated election law by working with third parties that targeted people more likely to support Democrats in voter registration drives, including illegal immigrants, in violation of campaign law.

“These alien registrations we’re finding on the voter rolls are coming from somewhere, and then when we learn this campaign is doing this, it really raises a serious question as to what sort of rate of illegal registrations they’re leaving,” said Mr. Adams.

Project Veritas Action has announced that it will continue to release undercover videos as part of its sting operation on Democrats involved with the Clinton campaign before the Nov. 8 election. Another video is expected to be posted Monday.