A liberal dark-money group that popped up in Maine earlier this year and has already spent at least $1 million in attack ads against four-term Republican Sen. Susan Collins is drawing new scrutiny.

A conservative-leaning watchdog group has filed an IRS complaint against Maine Momentum, a nonprofit whose leaders have direct ties to the state’s Democratic Party, as well as to Collins’ leading Democratic opponent, Sara Gideon.

In a letter to IRS Commissioner Charles Rettig, the Foundation for Accountability and Civic Trust, or FACT, argues that Maine Momentum is violating its 501(c)(4) nonprofit tax status by engaging in a “consistent pattern of activities and public admissions” that show it’s acting as an arm of the Democratic Party rather than serving the public good, as nonprofit tax laws require.

The complaint alleges that Maine Momentum, which calls itself a tax-exempt “grassroots advocacy effort” not required to disclose its donors, in reality is operating for the “substantial private benefit of the Democratic Party and Maine’s 2020 Democratic candidates for Senate instead of serving the public interest by promoting social welfare of the general public.”

Under IRS law, groups formed as 501(c)(4)s cannot stand in support or against any politician, whether done indirectly or directly. They are allowed to participate in minimal political activities, but those activities cannot be the sole focus of the organization.

Since the Supreme Court’s 2010 Citizens United case, which opened the floodgates for unions and corporations to spend unlimited amounts of money on ads and other efforts to influence voters, dark-money groups on the right and left have proliferated with little IRS regulation and enforcement.

When it comes to Maine Momentum, FACT argues that the organization is operating well outside the boundaries of the law.

“Section 501(c)(4) of the Internal Revenue Code maintains the integrity of social welfare organizations, as well as citizens’ confidence in their efforts,” Kendra Arnold, FACT’s executive director, said in a statement to RealClearPolitics. “These organizations are supposed to promote the social welfare of the general public not engage in overtly partisan politics, and there are many facts in this case which bring into question Maine Momentum’s execution of this requirement.”

The IRS complaint refers to quotes by one of the group’s leaders in a Portland Press Herald article describing its “sole focus” as “advocacy and accountability and public education” about Collins and her reelection campaign, part of a “multipronged strategy” by national Democratic operatives to defeat her.

The complaint also highlights several of the group’s direct ties to the Maine Democratic Party and Collins’ top Democratic opponent, Maine House Speaker Gideon. Christopher Glynn, the spokesman for Maine Momentum, had worked as recently as June for Gideon. Before that, he served as a spokesman for the Maine Democratic Party.

The group’s executive director, Willy Ritch, previously worked as the spokesperson for Maine Democratic Rep. Chellie Pingree. Lily Herrmann, the group’s community organizing and outreach director, also previously worked for the state Democratic Party and served as the co-president of the Colby College Democrats and chair of the Waterville Democratic Committee.

Hermann’s LinkedIn profile, the complaint notes, mentions her participation in a candidate training program run by Emerge Maine, a group that was forced to convert to a 527 political organization after the IRS denied its tax exemption in 2011 because its activities violated the private benefit rules for 501(c)(4) organizations by benefiting only the Democratic Party.

Emerge Maine also has strong ties to Gideon, who is a self-described alumna of the group’s 2012 program and has credited it for her start in politics. The group honored her as its “Woman of the Year” in June and its founder hosted a San Francisco fundraiser for Gideon’s Senate campaign in August.

Neither Maine Momentum nor the Gideon campaign immediately responded to a request for comment.

Maine Momentum has generated a flurry of media stories after it dropped $1.5 million in misleading attack ads against Collins over the summer. One of the television ads earned three Pinocchios from the Washington Post. It accused the centrist Republican of putting federal programs for seniors and retirees in harm’s way while giving big corporations massive tax cuts.

The ad quotes “David,” who says he’s a cancer survivor and calls on viewers to tell Collins to “stop risking” Social Security and Medicare.

Moments later, the ad asserts that Collins voted to give “tax breaks to corporations and then took donations from them.”

The Collins campaign has decried the ad as flat-out wrong, arguing that the longtime lawmaker worked to protect Medicare during the tax debate and tied her vote for the tax-cut package to a deal that included provisions ensuring that Medicare wouldn’t be jeopardized. After a lengthy explanation, the Post confirmed that the ad included “a significant factual error and/or obvious contradictions.”

Team Collins says the senator hasn’t taken money directly from corporations because doing so is illegal, although she does accept money from corporate political action committees, which she reports, as required, on her Federal Election Commission filings

It’s Gideon and the outside groups supporting her that aren’t being transparent about their funding, they counter.

“When the former Democratic aides who are running those ads are asked, ‘Who’s paying your salary?’ They have refused to say,” Collins said in the public radio interview in early September. “I think the people of Maine have a right to know. … Just as I have to disclose all of my contributions to the [Federal Election Commission], I think they should have to disclose the source of where their money is coming from, whether they are for me or against me. But [the ads] have all been against me so far.”

The FACT complaint also points out that Maine Momentum formed as a nonprofit in April 2019 but launched its public presence within a day of Gideon declaring her candidacy for the Senate, which took place June 24.

One week later, the complaint alleges, Maine Momentum launched the 16 Counties Coalition, a project to “pressure Republican Sen. Susan Collins on issues likely to resonate with moderate voters.”

Within the first two weeks of its launch, Ritch told the Press Herald that the group would be using “advertising, social media, and community organizing to encourage Collins to start putting families and working Mainers ahead of her special interest supporters.”

The complaint also cites the 16 Counties Coalition website as describing its mission in partisan terms.

“Our coalition is made up of concerned residents living with the consequences of the Republican-controlled Senate’s policies, which reward wealthy donors at our expense.”

Maine Momentum and the 16 Counties Coalition are also running digital ads and hitting Collins on Twitter and Facebook. Roughly 85% of the tweets by 16 Counties Coalition, the complaint alleges, have featured attacks on Collins and the only account the group’s Twitter handle follows is Collins’ Twitter account.