HELENA, Mont. — A non-partisan race for Montana Supreme Court has taken a distinctly partisan edge, with challenger Lawrence Van Dyke trying to cast Justice Mike Wheat as a liberal activist judge as his Republican backers pour tens of thousands of dollars into ads to support that message. Wheat and his supporters, in turn, have taken to the airwaves with their own ads, leading to a money battle in an election that is usually considered an afterthought on the ballot. The fight is a sad sign that the U.S …