The Senate blocked progress Tuesday on a bill that would keep the government fully operating past midnight Friday, led by Democrats who are vowing not to support any spending extension until Congress guarantees federal funding to address the drinking-water crisis in Flint, Mich. Flint relief has emerged as the crucial sticking point in negotiations on the stopgap spending extension necessary to avert an unusual election-year shutdown. Senate majority leader Mitch McConnell, a Kentucky Republican, unveiled a bill last week that addressed several Democratic demands, including a deal on Zika response funding and the elimination of several contentious policy riders. But it did not incorporate the $220 million Flint aid package that passed the Senate in separate legislation this month.