Washington (CNN) -- With the mid-term elections looming, the Supreme Court on Monday turned away from the opportunity to further loosen campaign finance restrictions, this time over disclosure of donors.
At issue was whether "political committees" -- unincorporated groups that make only "independent expenditures" -- can be required to disclose its donors.
The justices without comment rejected an appeal from SpeechNow.org, a conservative group that wanted to withhold certain information from the Federal Election Commission.
A federal appeals court in Washington ruled last March that the political organization could continue to raise and spend unlimited sums for independent campaign advertising, but must still regularly release the names of its donors, along with other information required by federal regulators.
Federal Election Commission figures show similar independent groups have spent more than a quarter-billion dollars in this election cycle, which ends with Tuesday's federal and state elections across the country.
That is about four times the amount poured into races in the last mid-term elections in 2006.
The federal appeals court had upheld SpeechNow.org's classification as a political committee, subject to a greater degree of regulation, under the sweeping McCain-Feingold federal law on campaign spending. FEC rules require these types of groups to register with the government if their "major purpose" is to get involved in federal election campaigns.
The group was created by the libertarian Cato Institute and the Club for Growth, an anti-tax advocate.
"Requiring disclosure of such information deters and helps expose violations of other campaign finance restrictions, such as those barring contributions from foreign corporations or individuals," said the unanimous 9-0 panel of the U.S. Court of Appeals for the District of Columbia Circuit.
David Keating, head of SpeechNow.org, had argued his group does not coordinate its activities with any political party or campaign and therefore should be subject to less restrictive disclosure requirements enjoyed by other politically active outside organizations.
The Obama administration had urged the high court not to get involved in the case.
The case is SpeechNow.org v. FEC (10-145).