The Supreme Court on Thursday struck down the "millionaire's amendment," a campaign finance law intended to level the field for House candidates facing wealthy opponents who spend lots of their own money.

The law says that when candidates spend more than $350,000 from their own pockets, opponents may qualify to accept larger individual contributions than normally allowed and can receive unlimited coordinated party expenditures.

The justices, in a 5-4 ruling that reflects skepticism of campaign finance overhauls, said the law violates the First Amendment.

"We have never upheld the constitutionality of a law that imposes different contribution limits for candidates who are competing against each other," Justice Samuel Alito wrote for the majority.

In dissent, Justice John Paul Stevens said that because the law "does not impose any burden whatsoever on the self-funding candidate's freedom to speak, it does not violate the First Amendment." Stevens highlighted the law's goal of fighting the perception that "congressional seats are for sale to the highest bidder."

At least 19 House candidates and nine Senate candidates have spent $350,000 or more of their own money on their campaigns so far this election cycle, according to figures from the Center for Responsive Politics, a Washington-based group that tracks political campaign money. In the 2006 elections, the number was 52 candidates.

In Nebraska, Democratic Senate candidate Tony Raimondo triggered the amendment this year, contributing $450,000 to his failed primary contest against Scott Kleeb.

Republican Pete Ricketts triggered it in 2006, contributing more than $12 million to his unsuccessful bid to unseat Democratic U.S. Sen. Ben Nelson.

The amendment's most prominent beneficiary so far has been Sen. Barack Obama. He was able to attract additional contributions for his 2004 Democratic senatorial primary campaign in Illinois because an opponent spent nearly $29 million of his own money.

The law has separate but parallel provisions for House and Senate candidates. The Senate provision was not at issue in this case.

Nonetheless, Michael Toner, former chairman of the Federal Election Commission, said he did not see "a basis for the government enforcing the Senate provision in light of this ruling."

Challenging the law was Jack Davis, a New York Democrat who so far has spent nearly $4 million of his own money in two losing campaigns for Congress and says he will spend $3 million more this year. Davis says it unfairly rewards his opponents by letting them exceed campaign fundraising limits simply because Davis tapped his fortune.

Alito said if the law raised the limits for all candidates, Davis' challenge "would plainly fail," raising the question of whether Congress could easily fix what the Court struck down.

Sen. John McCain, the co-author of the 2002 campaign finance reforms that contain the provision, expressed no interest in having Congress address the Court's decision.

McCain said the decision does not affect the Court's landmark ruling upholding the constitutionality of the soft-money ban prohibiting six-figure donations to political parties. The Republican presidential nominee-in-waiting said the millionaire's amendment was not part of the original legislation and was added on the floor during debate. The other co-author of the reforms, Sen. Russ Feingold, D-Wis., made the same point.

Adam Bonin, a lawyer who has handled election law cases, said self-financing candidates now can overwhelm their opponents with money in this year's elections. "Congress made a reasonable effort to try to level the playing field here, and the Court substituted its own judgment of what's fair," he said.

Chief Justice John Roberts and Alito, the most recently appointed justices, appear to be moving the Court away from its earlier backing of the 2002 political campaign reforms.

Alito succeeded Justice Sandra Day O'Connor, a decisive force in support of the reforms.

Last year, with Roberts and Alito aboard, the Court eased legal barriers against corporate- and union-financed television ads, saying free speech rights take precedence over government restrictions on political advertising.

Davis, the plaintiff in the latest ruling, lost in 2004 and 2006 to Republican Rep. Tom Reynolds, who spent more than $5 million in winning re-election two years ago, 51 percent to 49 percent.

Reynolds, who is retiring at the end of this term, chose not to solicit increased contributions after Davis triggered the millionaire's amendment. Reynolds could have received $6,900 from individual donors, triple the limit otherwise.

The case is Davis v. Federal Election Commission, 07-320.

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