BOSTON - Gov. Mitt Romney asked the state's highest court Tuesday if he has the power to fire the Massachusetts turnpike chairman after an engineer who led an investigation into leaks at the $14.6 billion Big Dig project says he can no longer vouch for the safety of its tunnels. "With the Big Dig there's been a pattern of cover-up and stonewalling that has left the public with little confidence that the project is being managed well or that the road and tunnel system are safe to travel," Romney said. But he stopped short of calling the tunnels unsafe and...