WASHINGTON (AP) — Vermont Sen. Bernie Sanders said Tuesday he has "zero doubt" that rank-and-file union members will support his Democratic presidential campaign even though Hillary Rodham Clinton has locked up many endorsements.Sanders joined labor activists on Capitol Hill to discuss new legislation to allow workers to join unions. He told reporters after the event that process for picking up labor endorsements isn't over "by any means" and he had the support of many workers in organized labor."Secretary Clinton has a lot of contacts with many of the union leaders over the years.