Amazon.com Inc.'s fierce resistance to unionization, skepticism among workers that organizing could get them a better deal and decisions on election parameters all contributed to the apparently lopsided defeat of a labor drive at the company's warehouse in Bessemer, Alabama, people close to the events said.

A vote by workers on whether to unionize failed on Friday by a more than 2-to-1 margin in a major win for the world's largest online retailer. The union plans to challenge the results based on Amazon's conduct during the election.

Union leaders had hoped the campaign just outside Birmingham would create Amazon's first organized workplace in the U.S. and spark a new era of worker activism. Instead, it has illustrated the continued challenges facing the labor movement in America.