The exit-voice tradeoff has helped scholars explain lower job satisfaction among union workers compared to nonunion workers since. Scholarship has further extended the exit-voice tradeoff to within-union samples by examining job satisfaction’s relationship to union participation instead of between union and nonunion workers. But how exactly does the exit-voice tradeoff apply to moderately or highly-satisfied union members? Are they participating in the union or is low job satisfaction a pre-requisite for union activism? This report, Union Participation and the Work Fit-Job Satisfaction-Nexus: A Study of the Chicago Teachers Union identifies the presence of a missing moderator that provides insight into the job satisfaction-union participation relationship. We suggest that the felt need to protect a job that is personally meaningful has inspired CTU members to become stronger, active union members. They are in effect using their union, not to preserve the best available job open to them, but to bridge the distance between the teaching profession’s aspiration and reality.