It appears the 501(c)(3) Friends of Elizabeth Street Garden, which has supported New York City Council candidate Christopher Marte, has grown into what is effectively a political action group, possibly in violation of federal, state and local laws, said experts consulted by City & State.

The group’s actions raised red flags and may be outright violations of laws barring campaign activity and substantial lobbying by tax-exempt nonprofits, according to several experts and a watchdog group. The experts reviewed research that was recently shared by a source on condition of anonymity and verified by City & State.

“For sure they should be investigated and someone should file a complaint about this,” said John Kaehny, executive director of Reinvent Albany and co-chairman of NYC Transparency Working Group. “I would suspect that they could face significant fines and penalties from the IRS, maybe lose their nonprofit status.”

The group’s efforts to save the Elizabeth Street Garden, a popular community garden in Nolita, played a pivotal role in galvanizing opposition to New York City Councilwoman Margaret Chin in the Democratic primary but may have crossed a legal line in its support for Marte, who is Chin’s opponent, and its criticism of Chin, charity experts said. Charities “are absolutely prohibited from directly or indirectly participating” in a political campaign, according to the U.S. Internal Revenue Service. Although federal authorities rarely investigate and penalize such behavior, experts said, the New York State Attorney General also has broad power to penalize and dissolve offending charities.

When asked for comment on whether the Friends of Elizabeth Street Garden were violating IRS rules, Jeannine Kiely, the group’s president, said that the nonprofit “did not intend to advocate in support of or in opposition to any candidate for public office, but instead to educate the public and interested parties about issues related to the Garden and our mission to preserve Elizabeth Street Garden as a unique public green, open space and NYC Park.”

RELATED: Key 2017 election contests to watch

Marte said he was surprised by the idea that the nonprofit had crossed a line in its advocacy.

“This is the first I’ve actually heard of this. It’s not really the Friends of the Eliz – it’s the individual people of the community,” Marte said, adding, “I don’t really agree with the whole, kind of like, ‘special interests of the garden affecting our campaign.’”

The distinction between individuals’ political support and the organization’s political support is an important one, experts said, because while leaders can legally be politically active, a charity cannot. Over time, it appears the line between leaders and the group itself has grown blurry and indistinct.

Residents rallying to save a garden created the nonprofit in 2014. It became increasingly politically active and partisan as one of their own – “Christopher Marte, Garden volunteer,” as he is identified in the group’s get-out-the-vote messages – and faced off against a New York City Council member who threatened the place that they loved.

Chin is one of the few sitting council members with a serious general election challenge. Marte, a community activist and former financial analyst, gave her a close race in the primary, and now he is back on the ballot in the general election on the Independence Party line. Marte’s platform is largely about criticizing Chin’s response to development projects in the district, including the NYU expansion, Rivington House and her support for building on the city-owned Elizabeth Street Garden site.

Marte told City & State that he grew up four blocks from the garden and used to volunteer there, befriending other people who loved the green space. Now, he said it has been one of the top issues in his campaign, because Chin’s desire to build on the plot is “a symbol of the current council office” in terms of “the lack of transparency, the lack of engagement, the lack of listening to the community” and looking at alternative sites for new senior housing.

A razor-thin margin of victory – just 222 votes – separated Chin from defeat in September’s primary. The garden is the reason his insurgent campaign performed so well, Marte told NY1, noting that he won 80 percent of the vote in the surrounding areas.

RELATED: Women lose ground in NYC Council, even if Chin wins

The garden plays a major role in the election, Emily Hellstrom, a board member for the nonprofit, told City & State in a recent interview. It has “galvanized people to vote for a change this year, vote for Christopher Marte,” Hellstrom said. “Because they know District 1 can do better.” Later, however, Hellstrom noted that Friends of Elizabeth Street Garden cannot participate in politics due to their 501(c)(3) status.

Friends of Elizabeth Street Garden has thrown its support to Marte, experts said, by praising him repeatedly while criticizing Chin in public statements by the organization and by inviting him and not her to events. A review of social media postings shows Marte attending at least eight of the nonprofit’s events, including “Wake Up Campaign” events, since May 2016. Chin has never been invited to a Friends of Elizabeth Street Garden event, according to a spokesperson from her campaign.

Kiely did not say whether the nonprofit ever extended invitations to Chin, but she did say that its events are open to the public and that anyone interested in attending is welcome.

"We have a broad mailing list that includes residents, small business owners, community and parks organizations and current and former staff members of city, state and federal officials, but all who are interested in attending our events are welcome,” she said. “This includes current and former staff for Chin."

While charities can organize candidate forums, they cannot host an event explicitly endorsing a candidate, said Allison Grayson, a policy director at Independent Sector who educates nonprofits on how to advocate for their causes within the rules. “You can walk really far up to the edge of something that looks like an endorsement and it’s still legal,” Grayson said. Still, there are limits. “The real issue is they need to invite both candidates.”

At a rally organized by the group in December 2016, Marte, holding a “Save the Garden” sign, called out to the crowd, “Where was she for the community? How can this be done in our neighborhood? Where is Margaret Chin?” The video of his remarks was posted on his Instagram account along with a link to his campaign website: “Visit martenyc.com and join the movement.”

The Friends of Elizabeth Street Garden, which began as a coalition of neighbors seeking to preserve the statue-studded garden, vociferously denounces Chin for her plan to develop the land as affordable senior housing and reduce the garden’s size. The charity appears to have grown increasingly politically active after it became frustrated that Chin would not change her mind.

RELATED: FPWA says Trump tax plan punishes working families

Hellstrom, the board member, said the group met with Chin in sit-down meetings and open hearings to talk about preserving the park long before the election, but could not change her mind. “We went through all the proper channels. And then we finally said you are not listening to us,” Hellstrom said. “It was just a complete stone wall. And we just said we’ve got to do a ‘wake up’ we’ve got to say, ‘You’re not listening.’”

The nonprofit has raised $73,329 to date for its “Wake Up Campaign,” to fund protests, outreach, banners, signs and messaging including email blasts to more than 6,000 members “to alert people who is for saving and who is for not saving the garden,” Hellstrom said. Considering the group’s support for Marte, experts noted that the New York City Campaign Finance Board and state Joint Commission on Public Ethics, which monitor lobbying, could deem the “Wake Up Campaign” and related activities to be unreported spending or spending exceeding legal limits, or that the organization itself is engaged in unregistered lobbying.

An email blast from the Friends of Elizabeth Street Garden on Sept. 12 with the subject line “It’s Primary Day, VOTE! Save the Garden” read, “Councilmember Chin will destroy the Garden. Each of her challengers will save it! Margaret S. Chin, our only local elected official who is committed to destroying the Garden, faces three challengers in the Democratic primary, all who support saving the Garden: Aaron Foldenauer. Dashia Imperiale. Christopher Marte, Garden volunteer endorsed by Garden supporter Downtown Independent Democrats.”

Kiely, the group’s president, has repeatedly endorsed Marte on her social media accounts. Also on Sept. 12, Kiely tweeted, “Campaigning for @ChrisMarteNYC since dawn!” Her Twitter bio first identifies her as “President, Friends of Elizabeth Street Garden,” but adds at the bottom, “Tweets and views my own.”

Nearly all the nonprofit’s leaders have financially supported Marte’s campaign, activity which is allowed. Seven of eight board members listed on the group’s website have made contributions totalling $6,430 to Marte’s campaign, according to city records. But one board member, Ilaria Fusina, appears to have violated the $2,750 campaign contribution limit by giving Marte $3,100, according to the New York City Campaign Finance Board website. Kiely said the donation had been refunded, which is reflected in the CFB's filings.

RELATED: Can David Greenfield join the Met Council? 

While the Chin campaign declined to comment on the record, some of the city councilwoman’s supporters are critical of the pro-garden nonprofit group’s activities.

Allen Roskoff, president of the Jim Owles Liberal Democratic Club, which endorsed Chin for re-election, said he was shown the same research shared with City & State. “Where there’s smoke there could be fire – I’m not accusing them of doing anything wrong,” Roskoff said, adding that authorities should look into the matter.

“If we get involved in specific races we abide by the campaign finance laws,” Roskoff said of his own political club. “We follow the rules and we expect everyone else to also.”

Editor’s note: This story has been updated with a comment from Jeannine Kiely indicating that anyone is open to attend events held by Friends of Elizabeth Street Garden, including current and former staffers of City Councilwoman Margaret Chin. The story has also been updated to reflect that campaign contributions by board member Ilaria Fusina that had exceeded limits were refunded.