Americans have come to detest Congress ever more deeply as it nears the end of a nasty fight over health care. But more than half still back President Barack Obama, a bright spot for a Democratic Party counting on its leader to help stave off expected losses in elections this fall. The latest Associated Press-GfK poll found that fewer people approve of Congress than at any point in Obama’s presidency. Support has dropped significantly since January to a dismal 22 percent as the health care debate has roiled Capitol Hill. Neither Republicans nor Democrats are safe; half of all people say they want to fire their congressman.