The Supreme Court agreed yesterday to referee a challenge to limits on pre-election ads, a key provision of the landmark campaign finance law that the court upheld in 2003. The justices will hear an appeal of a lower court decision that relaxed restrictions on mentioning candidates by name in issue ads run by corporations, labor unions and other special interest groups near the climax of a campaign. The court will hear the case in April and almost certainly decide it by July, well before the first presidential voting takes place in the Iowa caucuses next January.

Issue ads are those that do not purport to influence an election, but rather focus attention on an issue their sponsors find important. A provision of the McCain-Feingold law prohibits mentioning a candidate in issue ads in the 60 days before a general election and 30 days before a primary.

Its purpose was to end the common practice of circumventing limits on contributions in federal elections by airing ads that avoided expressly advocating a vote for or against someone while making clear a preference for, or more often, disapproval of one candidate.