The state ethics commission has taken a harder stand in recent months against groups that missed filing deadlines to report campaign expenses.

It's a stand we support, both because it preserves the integrity of the campaign financing system and because it underscores the importance of public disclosure.

In the most recent case, the commission fined the Maine Association of Realtors political action committee $10,000 for filing a report 20 days late. That penalty came on top of a $1,231 fine already paid by the Realtors PAC.

The PAC spent money on mailers to support two Republican state Senate candidates, both of whom were in close races. The group spent $2,969 in support of Christopher Rector of Thomaston and $3,186 in support of Lois Snowe-Mello of Poland.

By law, the PAC is required to report expenditures of more than $250 within 24 hours of making an obligation to spend the money. The Realtors PAC failed to do so until 20 days later.

In two other recent examples, the Maine Democratic Party was fined $5,000 for failing to immediately report expenditures on a mailer it sent in the same Senate race, this one in support of Democrat Deborah Simpson of Auburn, who ran against Snowe-Mello. The party argued that a mistake at the print shop, where the wording was changed on the literature without the party's knowledge, led to the reporting error.

And in November, the commission fined Fed Up With Taxes $10,000 for missing the deadline by just two days. An attorney for Fed Up With Taxes, the group that opposed beverage taxes to support Dirigo Health, said he was busy filing another report the same day this one was due. It was a large expenditure, $750,000, and the commission voted to impose the maximum fine because the public deserved to know about the expense the day it was made.

The Realtors PAC case, the one the commission voted on last week, is the most powerful example of why it's important for groups to strictly adhere to the reporting requirements.

It's not that there's any reason to think the Realtors PAC intentionally waited to file the report. A spokeswoman for the group made it clear she felt badly about the late filing and said it was an inadvertent error.

But by filing just days before the election, the PAC delayed important payments to the opposing candidates. That's because the candidates -- Simpson and David Miramant of Camden -- were entitled, under law, to receive matching money the same day the expense was reported to the ethics commission.

So instead of getting nearly $3,000 three weeks before the election, when he would have had time to put out a mailer of his own, Miramant got the money four days before voters went to the polls. For her part, Simpson would have been paid $3,186 on Oct. 11, giving her ample time to rebut the mailer.

Did the delay alter the outcome of the election?

As commission members discussed before voting 3-0 to impose the fine, it's impossible to know. Despite the late report, Simpson defeated Snowe-Mello by 108 votes. In the other instance, Rector, the Republican, defeated Miramant by nearly 2,000 votes.

In addition to raising the question of whether it influenced the election, the late filing also deprived voters of information they should have had 20 days earlier. Who's spending money on which campaign is all part of full disclosure that is an important part of the state's public financing system, the Maine Clean Election Act.

After all, if one of the goals of the clean election system is to make it clear where the money comes from, the public has a right to know that information as soon as possible.