If the toxic effects of outsize spending in judicial elections were not already evident, the fiasco playing out in the Wisconsin Supreme Court should erase any doubt.

Last month, a special prosecutor, who is investigating whether Gov. Scott Walker committed campaign-finance violations in the run-up to his 2012 recall election, formally asked at least one — and possibly as many as four — of the state’s seven justices to step aside when the court hears the case in April.

The prosecutor, Francis Schmitz, appointed by five Wisconsin district attorneys, cited “ethical concerns” as the reason for the unusual request. More precise details are not available because most of the investigation, which has been on hold for more than a year, is under seal until any charges are filed. But reporting by The Milwaukee Journal Sentinel has confirmed that the recusal request involves large amounts of spending by three conservative nonprofit groups in support of the elections of four of Wisconsin’s Supreme Court justices.

Those three groups — the Wisconsin Club for Growth, Citizens for a Strong America, and Wisconsin Manufacturers & Commerce — are at the center of the investigation looking into illegal coordination in fund-raising and spending between independent groups and Mr. Walker in 2011 and 2012.