For years, advocates of commuter rail have pushed the idea of a passenger train connecting Boston with at Nashua and Manchester, and even possibly Concord. But commuter rail has always bumped up against one huge, seemingly immovable object: money. It's not cheap to build such a system, roughly two-hundred-million dollars - and so the argument has long been that it's just not worth it, given all the other priorities New Hampshire has, including roads and bridges that need repair. However, this year, supporters are continuing their efforts, bolstered by rising business backing in the Southern Tier. And just recently, they urged a House Committee to keep four million dollars in the state's transportation plan to fund rail study and planning.