Over the Memorial Day weekend, many Mainers received a slick four-page mailer titled “Outdoors Maine” that featured a pretty picture of on its cover of the Katahdin Woods and Waters National Monument.

It also included a half page photo of Democratic congressional candidate Lucas St. Clair greeting a woman at her door followed by a write-up about the 2nd District hopeful’s effort to “revive Maine’s rural economy” by creating the national monument.

Though it arrived two weeks before the June 12 primary that may determine St. Clair’s future, it didn’t come from his campaign. It was instead a product of The Maine Outdoor Alliance, a group created this spring. Its only named official is Nathan Deyesso of Scarborough, who served as the best man at St. Clair’s 1999 wedding.

For Lewiston state Rep. Jared Golden, one of three Democrats competing in a June 12 primary, “It’s obvious their goal is to elect Lucas.”

Who is funding the group remains a mystery.

The outdoor alliance also paid for $300,000 in television advertisements in early May that prominently featured St. Clair as it touted the monument’s benefits.

It’s that sort of dark money spending that has raised concerns by St. Clair’s two opponents in the primary, Golden and Islesboro bookstore owner Craig Olson — and by St. Clair as well.

St. Clair has called for the group to stop its spending and disclose its donors. So far, it hasn’t.

“The campaign finance system is broken, and that’s true no matter who is doing the spending or what campaigns are supposed to benefit. We have to fix it,” St. Clair said.

Golden said St. Clair is “trying to pivot and deflect” instead of taking action to stymie secret donors from trying to swing the primary results.

Each of the Democrats vying for Maine’s 2nd District seat — the winner will take on U.S. Rep. Bruce Poliquin, a two-term Republican — insists he wants to reform the nation’s campaign finance system. They generally agree about what’s needed.

But spurred by the outdoor alliance’s spending, the issue has become a focal point of the race.

Golden released a television advertisement this week that’s airing in each of the three major markets in Maine that highlights his commitment to overturning Citizens United, the controversial 2011 U.S. Supreme Court case that opened the door to more secretive, outside spending in politics.

Featuring a dark image of St. Clair with storm clouds gathering behind him, the ad’s voiceover declares, “Jared Golden rejects dark money and will fight to repeal Citizens United because Washington should work for us, not special interests.”

St. Clair spokesman David Farmer said Golden is “attacking Lucas for actions that are being taken by an outside organization” even though the environmentalist has called for the outdoors group to end its advertising and name its donors.

“The attack is typical behavior by a politician and suggests that Rep. Golden believes he’s trailing in the race,” Farmer said.

Golden said the reality is that “Lucas got his hand caught in the cookie jar” and “isn’t walking the walk” when it comes to campaign finance.

Farmer said Golden “has a good story to tell about himself, but instead of talking about that he’s attacking. And, unlike what Rep. Golden implies, the ads do not advocate for Lucas’ election. That is simply not true.”

Golden said Thursday it is “completely laughable” that St. Clair insists he has nothing to do with the outdoor alliance when his best man runs it and people featured in its ads are also shown in the candidate’s own materials.

All three candidates back an array of proposed laws that would perhaps make a dent in the problem.

Golden said, though, that’s not sufficient.

“It’s not good enough to promise campaign finance reform while continuing to play by the rules of a system that is rigged to favor deep-pocketed, dark money special interests,” he said. “Only by holding our campaign finance practices and ourselves accountable to higher standards will we achieve the change we are fighting for.”

Olson said that “dark money has no place in this election. Not only does dark money muddy the waters of frank discussion, it gives amplifies the divide over which rational discussions should take place.”

He said his campaign is entirely grassroots driven, with donations only from individuals.

The campaign, Olson said, ought to be be about ideas “not about who can raise the most money, whether it is clean or dark.”

A group called End Citizens United has endorsed Golden. Its president, Tiffany Muller, said he is “a committed reformer who has a real record of working to limit the influence of big money in Maine.”

Farmer said that Golden’s legislative record doesn’t match his rhetoric, pointing to a handful of bills he argues would have required the disclosure of more donors to shadowy organizations and other campaign finance reforms.

Golden said the measures Farmer pointed to were unconstitutional in the wake of the Citizens United decision. That’s why the focus must be on reversing that ruling so that dark money donors like the Koch Brothers and whoever is behind the outdoors alliance will at least have a spotlight shown on their involvement.

Each of the congressional contenders, including Poliquin, file regular reports with the Federal Election Commission that detail each significant contribution they receive. The reports list the donors’ names, addresses and occupations.

Those reports are available online through the commission’s website.

scollins@sunjournal.com