In an election year, Congress’s work traditionally dwindles to one job: keeping the government running. This year is no exception, but with Washington more polarized than ever even doing that one thing is looking increasingly difficult. As Congress returns from Labor Day to face the last work period before the election, it faces an unwinnable conflict over spending that includes the real but remote chance of a shutdown. Democrats want a short-term funding bill that would keep the government running only through Christmas; Republicans want one that stretches until the spring.