“The federal government has shut down,” reads a new Baltimore Sun op-ed by political science professor Thomas F. Schaller. “And it’s the Republicans’ fault — period.” In contesting the House Republican’s use of legislation funding the federal government to block or alter the Affordable Care Act and its implementation, Schaller notes: The Constitution clearly establishes that a bill becomes a law if it passes both chambers of Congress and is signed by the president or if his veto is overridden by two-thirds supermajorities in both chambers. In 2010, Democrats in Congress passed, and President Barack Obama signed, the Affordable Care …