BERKLEY, Mich. (AP) - A federal prosecutor has quit his job to launch an independent candidacy for Michigan attorney general. Christopher Graveline (GRAV'-uh-lin) headed the violent crime unit at the U.S. Attorney's Office in Detroit, prosecuting gang members and drug traffickers. He faces a July 19 deadline to collect 30,000 signatures from voters to get on the November ballot. Graveline has support from Barbara McQuade, his former boss and a University of Michigan law professor. McQuade was U.S. attorney for eastern Michigan under President Barack Obama. McQuade says she's backing Graveline because of his skills as a prosecutor. Graveline believes the job of attorney general should be nonpartisan. If he gets on the ballot, he would face other candidates, including a Republican and a Democrat.