Last-ditch attempts by a group of Republican delegates seeking to stop Donald Trump from becoming the GOP presidential nominee are quickly fading -- and now their fight is facing a federal legal challenge. At issue is whether delegates to the Republican National Convention in Cleveland are bound to vote for the results of state caucuses and primaries. A group that claims the support of hundreds of convention delegates has been pushing to change Republican presidential nomination rules so that delegates can "vote their conscience" -- reviving a long-simmering debate led by GOP purists who believe that only convention delegates --...