A tea party group’s political message on a billboard here has unified local Democrats and Republicans, generating bipartisan criticism. The heads of the two parties here even used similar language in blasting the sign. “I say I’m appalled,” said Dale Stickel, head of the Elkhart County Republican Party. “I think it’s appalling,” said Shari Mellin, head of the Elkhart County Democratic Party. The message in question, from We the People of Marshall and Fulton Counties, a tea party group, appears on a billboard at the busy intersection of Nappanee Street and John Weaver Parkway, where Nappanee curves into Bristol Street....