The Democratic candidate for vice president will be in Marietta Tuesday evening for a downtown campaign event, officials said Saturday. Sen. Joe Biden of Delaware will speak at 7:15 p.m. in an outdoor rally in front of the former Ohio National Guard Armory on Front Street. “We’re the center of the universe, aren’t we?” said Molly Varner, chairwoman of the Democratic Party in Washington County. “There is a guarantee that the vice president will have passed through Marietta, we just don’t know if it will have been the Sunday candidate or the Tuesday candidate.” Biden’s campaign stop in Marietta follows a pass through today by the Republican candidate for vice president, Gov. Sarah Palin of Alaska, Sen. John McCain’s running mate. Few details of the Palin bus trip from Huntington to St. Clairesville were available on Saturday, other than speculation she might stop to stretch her legs or go through town without stopping. “What I heard from the campaign as of 3 p.m.