ACORN UPDATE: “The union-catspaw Working Families Party can strike fear into the hearts of New York politicians. But can it withstand some well-deserved legal scrutiny? Word broke on Tuesday that Manhattan-based US Attorney Preet Bharara has subpoenaed documents from the WFP — as well as from all the candidates who hired its campaign services this year. It’s about time: As The Post has reported for months, the party — an affiliate of the disgraced community organizers at ACORN — sports a shadowy, multi-layered structure that appears designed to conceal illegal activity.”