Sen. Jon Erpenbach, D-Waunakee, steps off the elevator to his latest hideout, a downtown Chicago hotel room he found for eighty bucks a night on Priceline.com. He steps into the hotel’s lime-green and gold lobby and makes a beeline for the free coffee and Kleenex. “I gotta blow my nose,” he says, and blows. Life on the run hasn’t been exactly glamorous for Erpenbach and the 13 other Democratic senators who fled Wisconsin Feb. 17 to prevent a vote on Gov. Scott Walker’s controversial budget repair bill. Their strategy relies on Senate rules that require a quorum of 20 legislators...