Vice presidential candidate Joe Biden told Pennsylvania delegates Thursday that running mate Barack Obama can't win the White House without the swing state. "This is not hyperbole: We cannot win without Pennsylvania," Biden said at a breakfast. Obama hopes Biden's working-class appeal will let him avoid a repeat of his Pennsylvania primary loss. Biden, who spent part of his youth in Scranton, Pennsylvania, often uses a just-folks speaking style that appeals to white, working-class voters - a group that Obama has struggled to persuade. During his contentious primary campaigns against one-time rival Hillary Rodham Clinton, Obama consistently failed to win over that voting bloc, which he must connect with if he wants to win the White House. Polling in Pennsylvania shows the race between Obama and McCain close. A Quinnipiac University poll conducted last week showed Obama with a 7 percentage point lead over McCain, but neither reached more than 50 percent. Obama's 49 percent support is likely to increase after a week of nonstop coverage of the Democratic National Convention here.