WHITE HOUSE President Bush is shrugging off the polls showing his job approval rating at low ebb. At a news conference with Iraq's visiting prime minister, Bush jokingly suggested the word "quagmire" to a reporter asking about a possible "second-term slump." The president says he knows U-S troops have a difficult mission in Iraq against a bloodthirsty and determined enemy. And he says on domestic issues, he's asking Congress to "take on some big tasks." He says he's not surprised his idea for a Social Security overhaul has met stiff resistance from lawmakers. Bush added: "This is a time of...