Union leader Paul O'Connor, who invited the vice president, said he wants Biden to see the collaboration between managers and workers to improve performance. Biden is a potential 2016 Democratic candidate for president and trips to the politically important shipyard have become a popular stop for those seeking their party's nomination. The 214-year-old Navy yard that repairs and overhauls nuclear submarines in Kittery, Maine, has survived three reviews from the Base Closure and Realignment Commission, including the most recent in 2005.