Presidential candidates may return contributions solicited for the general election campaign and accept public financing with its stricter limitations, the Federal Election Commission ruled Thursday.

By a 5-0 vote, the commission gave candidates the option of paying for their general election campaigns with private contributions or with taxpayer money from a presidential campaign fund.

The commission acted on the request for FEC advice from Democrati presidential candidate Barack Obama, the Illinois senator.

Commissioners hailed the decision as one way of helping to preserve a public financing system that is in danger of becoming obsolete.

"We all know the public financing system rests on a very fragile base," said commissioner Hans A. von Spakovsky.

Front-runners from both parties already have said they will reject public financing in the primaries, forgoing the spending limits that come with such funds. Several of the candidates have also said they are prepared to pass up the public money for the general election, believing they could raise far more than the $85 million available for each party's nominee.

Such a development would be the first time a presidential election would operate entirely outside the public financing system created in the post-Watergate era more than 30 years ago.

Obama's lawyers, in seeking the FEC's opinion, said he wanted to be able to raise private money for the general election while retaining the option of seeking a bipartisan agreement to only accept the public money.

The FEC on Thursday said he and the other candidates could do that provided they keep the general election money separate and return it to donors if they decide not to use it.