The 5-4 ruling affects the money that state and national parties can spend for advertisements, mass mailings and other activities in support of specific candidates.
The ruling does not directly affect the two central goals of the McCain-Feingold campaign finance overhaul: to ban "soft money" - the unregulated and unlimited donations that corporations, unions and individuals make to political parties - and to put restrictions on the political ads that special interest groups run in the final days of an election.
"Clearly, this decision demonstrates that McCain-Feingold restrictions on campaign contributions are constitutional," he said.
In two other cases, the high court upheld free-lance writers' rights to control electronic versions of their submissions to publications. And the court let stand a ruling that led Texas to end affirmative action at its public colleges and universities.
The court rejected the Colorado Republican Party's contention that government limits on such spending violate the First Amendment guarantee of free speech.
Allowing political parties to spend whatever they pleased in support of candidates would open the door to corruption, Justice David Souter wrote for the majority.
The court's more liberal wing won the vote of center-right Justice Sandra Day O'Connor to prevail. O'Connor's fellow swing voter, Justice Anthony M. Kennedy, joined the three conservatives, Chief Justice William H. Rehnquist and Justices Antonin Scalia and Clarence Thomas in dissent.
"Coordinated expenditures of money donated to a party are tailor-made to undermine contribution limits," Souter wrote.
The term refers to party spending done in concert with a particular campaign but kept separate from the candidate's coffers.
Largely eclipsed by unregulated soft money, coordinated expenditures are used less often now than when the case began with a dispute over radio ads in a 1986 Colorado Senate race.
The dissenters rejected the majority's finding that there is no real difference between this kind of party spending and direct contributions by individuals or political action committees.
"I remain baffled that this court has extended the most generous First Amendment safeguards to filing lawsuits, wearing profane jackets and exhibiting drive-in movies with nudity but has offered only tepid protection to the core speech and associated rihts that our founders sought to defend," Thomas wrote.
The ruling applies to party spending for House and Senate candidates, a category that totaled $427 million for Republicans and $265 million for Democrats in the 2000 elections.
Republicans stood to benefit more directly from an end to party spending limits, because of the historical fund-raising advantage the party enjoys.
GOP officials played down Monday's ruling, noting that it preserves a status quo in place since the Watergate era.
Sen. Mitch McConnell, R-Ky., one of the leading opponents of the McCain-Feingold overhaul, also discounted the ruling's effect.
"McCain-Feingold advocates can take no comfort in today's decision," because it dealt only with regulated "hard" money, McConnell said.
The McCain-Feingold measure has passed the Senate and is awaiting action in the House next month.
Senate opponents of the soft money ban and some others on both sides of the issue had predicted the court would rule the other way.
The cap on political party spending was originally passed as part of broad campaign money laws in 1974.
The FEC limits national and state parties to spending $33,780 apiece to help elect a House candidate. Senate limits are based on population and range from $67,560 for races in the smallest states to $1.6 million for California.
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