U.S. Senate Republican candidate Larry Hogan and the super political action committee that is funding a massive ad campaign to help him are facing a complaint that they engaged in improper coordination.

A Montgomery County voter filed a complaint with federal elections officials on Tuesday, alleging that the deep-pocketed super PAC Maryland’s Future violated the law by placing a prominent “donate” button on its webpage that goes directly to a fundraising page for Hogan’s campaign committee.

Under federal regulations, corporations — in this case the PAC — cannot use their resources to facilitate donations to candidate committees. Likewise, candidates can’t knowingly accept money that was improperly solicited, the complaint alleges.

The complaint was filed by Danielle Veith, a Montgomery County resident and registered Democrat, who wrote in the complaint that “this is no minor, technical violation.” She declined an interview request.

The complaint names Maryland’s Future, the Hogan for Maryland campaign committee and Hogan as an individual.

Veith’s complaint asks the Federal Election Commission to investigate whether Maryland’s Future improperly used corporate funds to solicit donations to the Hogan campaign, and whether the campaign knowingly accepted the funds.

“Given that the fundraising activity at issue all took place on a prominent public website that clearly states it is paid for by a super PAC, it is difficult to imagine how the Hogan campaign did not know,” Veith wrote in the complaint.

If the FEC finds a violation, the complaint asks for money to be refunded to donors and for fines to be levied.

A spokesperson for Maryland’s Future issued a statement Wednesday that called the complaint “frivolous” and highlighted a complaint made against Democratic candidate Angela Alsobrooks earlier this year.

That complaint, filed by the conservative group Americans for Public Trust in June, alleged that Alsobrooks used money from her state-regulated fundraising account to launch her federal campaign for the Senate.

An Alsobrooks advisor told the news outlet Politico at the time that the payments from her state account to her fundraiser around the time of her campaign launch were part of regular payments covering prior work done in Maryland. And Alsobrooks herself told the Washington Examiner that the complaint was “bogus.”

“Angela Alsobrooks is the only candidate in this race who has broken FEC rules,” Maryland’s Future spokesperson Lance Trover said in a statement. “Maryland’s Future is in full compliance with the law and abides by all the Federal Election Commission regulations and guidelines. This is a frivolous complaint, and we are confident it will be dismissed.”

Hogan’s campaign did not immediately respond to questions about the complaint.

Hogan and Alsobrooks are vying for a U.S. Senate seat from Maryland that is up for election this year following longtime Democratic U.S. Sen. Benjamin Cardin’s decision not to run again.

Alsobrooks, currently in her second term as Prince George’s County executive, has been leading in recent polls over Hogan, a former two-term governor. The race has drawn national attention and tens of millions of dollars in ad spending — with Maryland’s Future as the biggest spender — because it could influence the balance of power in the Senate.

Democrats hold a 51-49 edge that they hope to preserve, while Republicans are hoping to flip enough seats to gain control. While some other states’ Senate races appear to be closer, Maryland’s is competitive enough to factor in the national political conversation.

Voting by mailed ballot is already under way, with in-person early voting from Oct. 24 through Oct. 31, followed by traditional Election Day voting on Nov. 5.