WASHINGTON — The Supreme Court stepped into a sensitive dispute Friday over a state judge's decision to participate in a case that involved a key campaign supporter.

The justices typically avoid cases about judicial ethics, but they agreed to review the actions of a West Virginia Supreme Court justice whose vote overturned a $50 million verdict against a company that is run by the most generous backer of his election.

The action comes amid growing concern over the role of money in electing state judges.

Don Blankenship, the chief executive of Massey Energy Co., spent more than $3 million to help elect Justice Brent Benjamin to the West Virginia high court. Benjamin twice was part of 3-2 majorities that threw out a verdict in favor of Harman Mining Co. in its coal contract dispute with Massey.

Harman said Benjamin's participation in the case created an appearance of bias strong enough to violate its constitutional rights.

The American Bar Assocation and other legal ethics groups have taken Harman's side.

In earlier cases, the Supreme Court has said that judges must avoid even the appearance of bias.

Benjamin repeatedly rejected calls to recuse himself from the case when it was before the state high court. He has since said that he fairly judged the dispute.

Benjamin issued a lengthy defense of his actions, pointing out that he had no financial interest in the outcome of the case and the campaign money went to an independent group, not his campaign.

The Supreme Court case stems from a jury verdict in 2002 that concluded Richmond, Va.-based Massey hijacked a coal supply contract from Harman, plunging both it and founder Hugh Caperton into bankruptcy.

Massey contended Harman filed for bankruptcy because of mounting losses at a mining facility and other problems that had nothing to do with Massey.

Arguments will take place in March or April.

The case is Caperton v. Massey, 08-22.