Why did the face in the Oval Office change but the policies remain the same? Critics tend to focus on Obama himself, a leader who perhaps has shifted with politics to take a harder line. But Tufts University political scientist Michael J. Glennon has a more pessimistic answer: Obama couldn’t have changed policies much even if he tried.Though it’s a bedrock American principle that citizens can steer their own government by electing new officials, Glennon suggests that in practice, much of our government no longer works that way. In a new book, “National Security and Double Government,” he catalogs the ways that the defense and national security apparatus is effectively self-governing, with virtually no accountability, transparency, or checks and balances of any kind. He uses the term “double government”: There’s the one we elect, and then there’s the one behind it, steering huge swaths of policy almost unchecked. Elected officials end up serving as mere cover for the real decisions made by the bureaucracy.