The Washington Post-ABC poll suggests that widespread concerns about the state of the economy continue to make President Obama vulnerable, despite questions about the quality of the GOP field. The survey shows that Romney, who formally launched his economy-focused campaign last week, is starting off strong. The poll showed Obama leading five other potential rivals but in a dead heat with Romney, each with 47 percent among all Americans. But among registered voters only, the poll put Romney ahead, 49 percent to 46 percent.