"Opposition can be a self-perpetuating force. Once one local turns it down, others will be willing to vote 'no,' " said Gary Chaison, a professor of industrial relations at Clark University in Worcester, Mass.

Friday, the four-year tentative agreement narrowly was defeated by workers at Detroit Axle, Local 961, and Chrysler Twinsburg, Ohio, Local 122, the Detroit News reported. Thursday, the pact was rejected by workers at the St. Louis North Assembly plant.

"I was totally floored," Local 961 President Ed May said Friday night. "For that membership to turn that down, I was appalled."

Three other locals, including an engine plant in Kenosha, Wis., have approved the pact with voting to end nationwide Wednesday, the Detroit Free Press reported.

The sticking points appear to be a two-tier wage system in which new hires would be paid less and the lack of specific product commitments for Chrysler plants, the Free Press reported.