PITTSBURGH Teresa Heinz Kerry joked about being a loose cannon when she campaigned for her husband today at a Pittsburgh library. "No one can ever hear me," the soft-voiced 65-year-old wife of Democratic presidential nominee John Kerry said, fiddling with her microphone. "But when they do, watch out!" -- she joked.Heinz Kerry's appearance at the library, and a get-out-the-vote rally at Penn State's main campus tonight will wrap up a two-week swing through Pennsylvania for Senator John Kerry's wife.The tour wrapped up just as polls released by Quinnipiac (kwin-uh-PEE'-ak_ University and A-B-C News show that President George W. Bush has...