(AP) — President Barack Obama’s re-election campaign is barely a month old, but Camille Gervasio and other volunteers nationwide already are hard at work. ”Are you with us? Are you in?” Gervasio asks into her iPhone, dialing through a call sheet resting on her laptop to line up supporters for an election 18 months away. In call centers like this one on the eighth floor of an office building, the president’s backers are trying to take advantage of a head start over the still-forming Republican field and the benefits of incumbency to rebuild a grassroots effort that mobilized millions of voters in 2008. Obama’s campaign has pledged to reach out to every voter it was in contact with during his first run, a herculean 50-state organizational effort to reconnect with its supporters — some of them now disillusioned with the president because of his policies — while giving it an early indication of any vulnerabilities among critical constituent groups.