WASHINGTON — Swift Boat Veterans for Truth and MoveOn.org Voter Fund, two outside groups that played key roles in the 2004 presidential election, have reached an agreement with the Federal Election Commission to pay nearly $450,000 for various violations.

The groups, along with the League of Conservation Voters, settled charges that they failed "to register and file disclosure reports as federal political committees and accepted contributions in violation of federal limits and source prohibitions," the FEC said in a Dec. 13 statement.

The commission approved the three settlements on a vote of 6-0.

The FEC's unanimous decision to approve the agreements goes to the heart of campaign tactics that reached full bloom in the 2004 campaign. At issue was the emergence of nonprofit political groups, called 527s based on the section of the Internal Revenue Service code that governs their activities, operating as independent campaigns attacking Democratic nominee Sen. John Kerry or President Bush.

The group listed as Swift Boat Veterans and POWs for Truth will pay $299,500. In the 2004 campaign, the group spent $20.4 million criticizing Kerry's military record in Vietnam. Many of the group's claims about Kerry's service were never substantiated.

MoveOn.org Voter Fund will pay $150,000. The liberal organization challenged President Bush on various issues in the campaign. The group spent $14.6 million on television ads attacking Bush's record.

The League of Conservation Voters will pay $180,000. The group ran ads against Bush and other federal candidates, criticizing their stands on environmental issues.

The civil penalties were the first of this magnitude since the Supreme Court upheld most of the campaign-finance law passed by Congress in 2002 that barred political parties from raising unlimited amounts of money from corporations, unions and wealthy individuals.

The FEC concluded that the three 527 organizations violated campaign-finance laws because they expressly stated their desire to influence the presidential election in their fundraising, their public statements or their advertisements. Such activity, the FEC said, could only be conducted by political committees registered with the FEC that abide by contribution limits and public-disclosure requirements.

Commission Chairman Michael Toner said the penalties sent a "strong message" and set "important touchstones for the future."

"This will have significant implications for the 2008 presidential race," he said. "527 organizations are on clear notice about what their legal obligations are."

But campaign-finance watchdog groups said the FEC's actions were "too little, too late," in the words of Paul Ryan of the Campaign Legal Center.

The center and other organizations like it have been calling on the FEC to adopt specific regulations governing 527 groups. The FEC in 2004 refused to enact such rules, arguing that it would deal with the groups on a case-by-case basis. Several other complaints involving 527 groups are pending before FEC.

MoveOn.org shut down its Voter Fund organization in 2004, and drove its campaign activity through its political action committee, which raised more than $27 million in the 2006 election cycle.

"We welcome the FEC clamping down on pop-up 527s, set up just to influence elections and funded only by big money, since that would almost certainly put Swift Boat Veterans and similar groups out of business," said Wes Boyd, a co-founder of MoveOn.org.

Lawyers for the Swift Boat Veterans told the FEC that they acted with "good-faith belief" that their communications were not affected by the campaign-finance law. They argued that by not adopting specific rules in 2004, the FEC had left the law murky.

"It is far better to end this legal confrontation now rather than continue a costly battle against government bureaucrats in an area where the law is unconscionably vague," retired Rear Adm. Roy Hoffmann, founder of the Swift Boat Veterans, said in a statement.