Both President Obama and Mitt Romney share a similar goal when it comes to the federal debt: They want to get it under control. How they would do it differs greatly. Obama’s goal is more restrained; he wants to keep deficits from growing faster than the economy. Romney’s aim is to flat-out balance the federal budget in eight years. Unfortunately, budget experts say, both candidates’ plans fall short. “Obama’s numbers are more realistic, but they don’t get us very far,” said Robert Bixby, who runs the Concord Coalition, a deficit watchdog group. “Romney’s numbers get us a long way, but they aren’t very realistic.”