AUGUSTA, Maine — A year after an out-of-state campaign group was hit with the largest ethics fine in state history for failing to disclose its donors until after the election, opponents of this fall’s Question 1 were penalized Tuesday for using a similar tactic.

The Maine Ethics Commission levied a $3,251 fine against Secure Maine Voters, the political action committee urging a “no” vote on Question 1 to maintain a recent ban on same-day voter registration, for not filing an expenditure report on time.

According to Cindy Sullivan with the ethics commission, Secure Maine Votes spent $162,000 on television advertising on Oct. 28. The expenditure report, however, was not filed until Monday, Oct. 31.

During the last 13 days leading up to an election, Maine law requires political action committees to file reports on any expenditures of $500 or more within 24 hours of the expenditure. PACs are not required to report contributions received in that same period.

In recent days, Secure Maine Votes spent about $300,000 even though its most recent campaign finance report, on Oct. 25, showed only $36,000 in donations.

Jonathan Wayne, director of the Maine Ethics Commission, said that’s because contributions made after Oct. 25 do not have to be disclosed until after the election.

“It’s not unusual for PACs to get a large infusion of cash in the last few weeks to get their message out to voters,” Wayne said Tuesday. “But I think there is a feeling that people should know where that money comes from.”

Tuesday’s penalty throws a new element into the battle over Question 1 and the future of Election Day registration in Maine.

Question 1 asks: “Do you want to reject the section of Chapter 399 of the Public Laws of 2011 that requires new voters to register to vote at least two business days prior to an election?”

Both sides have been spending a lot of money in the final days before the Nov. 8 election.

Protect Maine Votes, the PAC calling for a “yes’’ vote, spent about $250,000 on TV ads on Oct. 28, according to expenditure reports filed with the Maine Ethics Commission.

Donations to the Yes on 1 campaign have been well-documented since August, shortly after the petitions were certified to get the question on the ballot.

As of Oct. 25, the campaign had raised nearly $500,000, with nearly $300,000 coming from one donor, Donald Sussman, a well-known Wall Street hedge fund manager, husband to Democratic U.S. Rep. Chellie Pingree and longtime financier of progressive political causes in Maine.

David Farmer, spokesman for Protect Maine Votes, said Sussman’s contributions have been disclosed, as have smaller donations made by more than 400 individuals and organizations.

“We’ve been transparent with where our money has come from and we’re proud of that support,” he said.

Protect Maine Votes already had spent more than $400,000 through Oct. 25. That had all been documented with the ethics commission.

By comparison, Secure Maine Votes, the No on 1 campaign, has spent about $300,000 just since Oct. 27 with the largest expenditure going to pay for the television spot. The rest was spent on direct mailers, robo-calls and polling, according to expenditure reports filed in the last week.

Asked to provide an explanation for the late spending and lack of disclosure on contributions, Jen Webber, spokeswoman for the No on 1 campaign, provided this statement:

“The fascination with the idiosyncrasies of campaign finance reports is just the kind of politics as usual that the people of Maine are sick of,” she said. “The No on 1 campaign is concerned with one thing — preserving the integrity of Maine’s elections. It is Politics 101 that the majority of expenditures occur in the last week of an election.

“Obviously, our opponents are concerned that our message in gaining traction, despite the hundreds of thousands of dollars that Wall Street Hedge Fund Baron Donald Sussman is using to try to make Maine’s elections less secure.”

Webber did not respond to requests for comments about Tuesday’s ethics commission fine by early Tuesday evening.

Maine Democratic Party Chairman Ben Grant had a different take on the late activity by Secure Maine Votes.

“There can only be one answer: They don’t want people to know who’s funding their campaign,” he said. “The most bothersome point is that they can fund their entire opposition and no one will know who’s putting up money until after the election.”

This isn’t the first time late money has played a role in Maine elections recently.

In the final days before the November 2010 election, the national Republican State Leadership Committee spent $400,000 on negative mailers distributed to voters in five Maine Senate districts where Republicans were running close races.

Those expenditures were different because the lack of reporting denied Democratic candidates matching funds in time to use them.

The Maine Democratic Party filed a complaint that prompted ethics commission members to conclude that the expenditures violated the Maine Clean Elections Law.

The Republican State Leadership Committee was fined, but by then it didn’t matter.

In all five races where mailers were distributed in the final days, the Republican candidate won, allowing the Maine Senate to flip from Democrat to GOP control.

Before that election, during the 2010 legislative session, the Maine Ethics Commission introduced a bill, LD 1546, that would have required PACs and party committees to report within 24 hours contributions, in addition to expenditures, greater than $1,000 that came within the last 13 days before an election.

The Legislature enacted portions of the bill, but not the proposed addition of contributions to the 24-hour reporting requirement.