AUGUSTA, Maine — The Maine Ethics Commission on Wednesday fined the National Organization for Marriage $2,000 for the late filing of a campaign finance report that detailed $800,000 in contributions from the Washington, D.C.-based group to the lead campaign opposing this month’s ballot initiative to legalize same-sex marriage.

The ethics commission cited the organization — which is active in campaigns opposing same-sex marriage across the country — for missing the Oct. 26 deadline for a campaign finance report by 14 hours.

“As much as we’ve had our struggles with NOM, we have to treat them fairly and consistently,” said Walter McKee, the commission chairman. “It’s a large organization, and $2,000 is in the zone.”

The Maine Ethics Commission initially levied an $8,000 penalty on the group based on penalty guidelines detailed in state election law, but commission staff members recommended a 75 percent reduction in that amount after an NOM lawyer asked for a waiver of the fine.

The fine levied against NOM doesn’t mark the first time the group has been at odds with the Maine Ethics Commission. The ethics commission and NOM became involved in a protracted court battle following Maine’s 2009 ballot initiative that overturned a same-sex marriage law passed by the state Legislature.

The organization chipped in $1.9 million for anti-gay marriage efforts that year, but didn’t disclose the source of its funds, which it had raised specifically for Maine’s ballot initiative campaign.

NOM challenged the ethics commission in federal court after the commission determined state law required the organization disclose its donors. A federal judge in 2011 upheld the constitutionality of Maine’s campaign finance disclosure laws. The U.S. Supreme Court twice this year declined to hear separate NOM appeals.

The high court’s refusal to hear NOM’s case effectively allows the Maine Ethics Commission to move forward with an investigation into the group for its 2009 activities in Maine related to that year’s same-sex marriage ballot initiative.

NOM contributed about $1 million to anti-gay marriage efforts in Maine this year. The organization, however, said it didn’t raise the funds specifically for the Maine campaign and didn’t have to disclose individual donors as a result.

In its request for a waiver of the late report penalty, a NOM lawyer said the group “made a bona fide effort to file the report on time.”

“The report was prepared in a timely fashion, but was inadvertently not submitted by oversight,” lawyer Joseph Vanderhulst wrote in a letter to the ethics commission. “As soon as the oversight was noted, the report was filed.”

Vanderhulst also argued that “there was no harm at all suffered by the public from the late disclosure” since Protect Marriage Maine, the campaign that received the contributions, already had made them public through its campaign finance reports. Ethics commission staff members agreed that the public suffered no harm from the late filing and recommended reducing the penalty.

The NOM report detailed three contributions totaling $800,000 from the national organization to its Maine political action committee, and three contributions in the same amounts from the political action committee to Protect Marriage Maine. The report also showed $111 in bank wire fees and $1,850 in unpaid obligations for legal and bookkeeping services.

Maine’s same-sex marriage initiative passed earlier this month with support from 53 percent of voters.