By a 5-4 vote in a case from West Virginia, the court said that a judge who remained involved in a lawsuit filed against the company of the most generous supporter of his election deprived the other side of the constitutional right to a fair hearing.

"Just as no man is allowed to be a judge in his own cause, similar fears of bias can arise when — without the consent of the other parties — a man chooses the judge in his own cause," Justice Anthony Kennedy said for the court.

With multimillion-dollar judicial election campaigns on the rise, the court's decision Monday could have widespread significance. Justice at Stake, which tracks campaign spending in judicial elections, says judges are elected in 39 states and that candidates for the highest state courts have raised more than $168 million since 2000.

"Judicial elections have become more expensive, more negative and more subject to influence by special interest groups," said Chief Justice Margaret Marshall of Massachusetts, president of the Conference of Chief Justices.

The West Virginia case involved more than $3 million spent by the chief executive of Massey Energy Co. to help elect state Supreme Court Justice Brent Benjamin. At the same time, Massey was appealing a verdict, which now totals $82.7 million with interest, in a dispute with a local coal company. Benjamin refused to step aside from the case, despite repeated requests, and was part of a 3-2 decision to overturn the verdict.

The coal company, Harman Mining Co., and its president, Hugh Caperton, took the case to the high court.