By LIZ SIDOTIWASHINGTON (AP) ¿ Barack Obama's optimistic campaign rhetoric has crashed headlong into the stark reality of governing. In office two months, he has backpedaled on an array of issues, gingerly shifting positions as circumstances dictate while ducking for political cover to avoid undercutting his credibility and authority. That's happened on the Iraq troop withdrawal timeline, on lobbyists in his administration and on money for lawmakers' pet projects. "Change doesn't happen overnight," Obama said at a town-hall style event in California on Thursday, seeming to acknowledge the difficulty in translating campaign pledges into actual policy. Asked by a campaign volunteer how his supporters can be most effective in helping him bring the sweeping change he promised, Obama said: "Patience." The event was part of a weeklong media blitz that Obama had hoped would help sell his budget ¿ the foundation of the health care, education and energy changes he promised in the campaign. But his budget message was overshadowed for much of the week by the public furor over $165 million in executive bonuses paid by American International Group Inc. after the insurance giant had received billions in federal bailout funds.