A group including former leaders of the fledgling union that organized an Amazon warehouse in New York is suing the union, accusing it of violating its own constitution and asking the court to force an election for union officers. The complaint, filed Monday in U.S. District Court of the Eastern District of New York, comes as the upstart Amazon Labor Union – the only certified group representing Amazon workers – struggles to recapture the momentum that led to its surprise victory last year following a series of setbacks. Since that win, the group has lost union elections at two other Amazon facilities and abandoned efforts at a third warehouse in California.