Campaign finance reform emerged as a major theme of the coming Supreme Court term yesterday, as the justices announced that they will rule on federal and state efforts to regulate campaign-season advertising by advocacy groups and to limit spending by candidates.

The cases present the court with its first opportunity to revisit key constitutional issues in campaign law since it issued a 5 to 4 decision in 2003 upholding the Bipartisan Campaign Reform Act, known as the McCain-Feingold law or BCRA.

Yesterday's decisions were produced by an eight-member court, because John G. Roberts Jr. has not yet been confirmed by the Senate to succeed the late Chief Justice William H. Rehnquist. They came out of the annual "long conference," at which the court considers thousands of appeal petitions that have accumulated during its summer recess.

Justice John Paul Stevens, the senior associate justice, presides over the court in the absence of a chief justice.

The first case is a challenge to provisions of the 2002 McCain-Feingold campaign law that prevent corporations or labor unions from buying ads with unregulated money about a specified candidate in the weeks just before an election.

Wisconsin antiabortion activists say their particular proposed ads are genuine efforts to express their views on an issue, not attacks on candidates disguised as issue ads -- or "sham" issue ads the law was meant to regulate.

A three-judge panel of the U.S. District Court in Washington ruled last year that the Supreme Court's 2003 ruling upholding McCain-Feingold precluded such a case-by-case effort to avoid the law's provisions. The Bush administration urged the Supreme Court to uphold that decision without a hearing, which the high court could have done if five justices had agreed.

McCain-Feingold was upheld 5 to 4 in 2003. Justice Sandra Day O'Connor was a member of that majority but will leave the court as soon as a successor is confirmed by the Senate.

"O'Connor was the swing vote" in that case, said Rick Hasen, a specialist in election law at Loyola Law School in Los Angeles. "This could provide the vehicle for a more conservative court . . . to reverse that aspect" of the 2003 decision.

The case is Wisconsin Right to Life, Inc. v. Federal Election Commission, No. 04-1581.

The second case accepted yesterday involves three consolidated challenges to a 1997 Vermont law that puts a ceiling on how much a candidate for state office can spend. Under the law, candidates for governor may spend no more than $300,000 per two-year election cycle. Candidates for lieutenant governor may spend no more than $100,000, and smaller limits apply to other offices.

The U.S. Court of Appeals for the 2nd Circuit, based in New York, upheld the Vermont law last year, ruling that the law was carefully designed to meet compelling needs to avoid political corruption, or the appearance of corruption, and to prevent fundraising from taking too much of politicians' time and attention.

But Vermont's Republican Party and other political activists say the law violates their constitutional right to free speech. They note that the Supreme Court struck down expenditure limits on First Amendment grounds in its landmark 1976 decision Buckley v. Valeo, and they argue that the 2nd Circuit was wrong to find that Buckley left some room for laws like Vermont's.

Supporters of campaign spending limits, including 13 states, a bipartisan group of eight U.S. senators, the NAACP and 17 current and former state judges, urged the court to hear the case.

But Hasen said this strategy may backfire, because it is likely the court took the case to reverse the 2nd Circuit's ruling.

Two other appeals courts had previously struck down expenditure limits, he noted, but the Supreme Court did not decide to review those rulings.

The consolidated cases are Randall v. Sorrell, No. 04-1528; Vt. Republican State Committee v. Sorrell, No. 04-1530; and Sorrell v. Randall, No. 04-1697.

Oral arguments are expected in January and decisions by July.