Justice Clarence Thomas’s influence was on full display in the Supreme Court’s landmark decision to strike down a key campaign finance restriction. And it’s just one in a string of cases in which Thomas could be dragging the court toward his way of thinking. Chief Justice John Roberts penned Wednesday’s plurality decision, which eliminates the limit on the total dollar amount an individual may give to political candidates and committees.But Thomas, seen by many as the court’s most conservative justice, wrote a concurring opinion that both represented the decisive vote in the 5-4 decision, and beckoned the justices to go further.Thomas...