Montana Republicans are asking the U.S. Supreme Court to step in as early as this week and force the state to “close” its upcoming primary so only GOP voters can participate -- in a case that could pose complications for Donald Trump. The Republican front-runner so far has done better in "open" primaries, where members of both parties can vote, than in "closed" primaries limited to Republican voters only. Montana, set to vote June 7, has had an “open primary” since 1912. But state GOP officials want to change all that, in a bid to keep out Democrats and other...