Democratic voters in the Second Suffolk and Middlesex District aren’t just choosing among four candidates for state Senate Tuesday; they’re also deciding among distinct visions of how government should operate. All four candidates believe state government can improve the lives of Massachusetts residents. The best choice for the seat, state Representative Will Brownsberger of Belmont, has a progressive record on social and environmental matters - but also a history of creative thinking about making government more effective, honest, and transparent.