Maine’s campaign finance watchdog is reviewing the use of a controversial messaging tactic by three Democratic candidates for governor.

An attorney and former deputy attorney general for the state complained to the Maine Commission on Governmental Ethics and Election Practices about the use of “red boxing“ by Nirav Shah’s campaign last week. The Shah campaign responded by asking the commission to also look into the tactics of Hannah Pingree and Troy Jackson’s campaigns.

The complaints are on the agenda for Wednesday’s commission meeting.

Red boxing refers to messaging that a campaign may post on its website — often in a red box — using specific language that goes beyond simply stating a candidate’s positions in order to invite outside groups to advertise on the candidate’s behalf.

In most cases, it is illegal for candidates to suggest a supportive group advertise for them, because the money to do so would almost certainly amount to a contribution that exceeds spending limits. That’s according to a memo Jonathan Wayne, executive director of the commission, wrote to commissioners Thursday.

The current limits on contributions to candidates for governor is $2,075 per election.

James Kilbreth, an attorney and former chief deputy attorney general for the state, filed a complaint last week asking the commission to investigate the Shah campaign for red boxing. Kilbreth pointed to a lengthy statement included in a red box on Shah’s website.

Maine voters “should watch while on the go and read, that Dr. Nirav Shah is the leader our state needs to stand up to Donald Trump and deliver real results on affordability — especially likely voters in the Portland media market,” the statement says in part.

Kilbreth said in his complaint that the statement “raises numerous red flags.”

He said he was told by people who know campaign advertising that to advertisers, the language would read as a set of instructions for running an ad on behalf of Shah.

Kilbreth said the post raises legal questions, and asked the commission to investigate whether the message resulted in any illegal contributions to Shah exceeding the $2,075 limit.

Newell Augur, an attorney for the Shah campaign, then asked the commission to investigate red box statements by Pingree and Jackson after being informed of Kilbreth’s complaint.

“There are other Democratic gubernatorial campaigns currently engaged in this common practice,” he wrote in a letter to Wayne.

In an email Thursday, Kilbreth said he brought his complaint because in his years of work as an attorney he often represented both campaigns and independent expenditure groups.

“I believe one of the few ways to deal with the obscene amounts of money the Supreme Court has allowed dark money PACs to spend in elections is to ensure that such PACs can’t coordinate with candidates’ campaigns,” he wrote.

Wayne wrote that red boxing itself isn’t illegal, but it could result in violations of the law if an outside group used the messaging to spend more than $2,075 in the governor’s race. He wrote that red boxing is “not necessarily safe in Maine state elections” even though the Federal Election Commission has indicated it won’t prosecute it at the federal level.

When the commission takes up the complaints Wednesday, staff are recommending that they take an “educational approach” rather than enforcement against the three Democrats. Wayne said neither complaint showed red boxing resulted in any specific spending by the candidates, and Pingree appears to have removed her campaign’s red box messaging.

The commission could approve an advisory statement warning about the risks of red boxing, or members could draft other guidance if they feel that red boxing should be protected under the First Amendment and not viewed as a potential violation of contribution limits, Wayne said.

Kayla van Wieringen, Shah’s campaign manager, said in a written statement Thursday that the campaign is confident that their approach “is fully consistent with Maine law and the ethics commission’s own guidance.”

“We welcome the commission’s guidance as we follow whatever recommendations they set forth,” she said.

Spokespeople for Jackson and Pingree’s campaigns did not respond to requests for comment.