Last year, the workers of Republic Windows and Doors successfully brought back the sit-down tactic, providing one of the few sunny spots in the unrelenting gloom that is the American labor movement. The maneuver seems to be catching on as factories close and jobs become vulnerable. Last week, unionized workers at Hartmarx Suits in Chicago -- where Obama gets his impeccably tailored threads -- voted to stage a sit-in if the factory isn’t sold to someone who will preserve their jobs.