It is the question that has hung over Senator Barack Obama’s presidential campaign, and it loomed large on Tuesday night after his loss to Senator Hillary Rodham Clinton in Pennsylvania: Why has he been unable to win over enough working-class and white voters to wrap up the Democratic nomination? Lurking behind that question is another: Is the Democratic Party hesitating about race as it moves to the brink of nominating an African-American to be president? Mr. Obama remains ahead of Mrs. Clinton in delegates, in the popular vote and in national polls, and Mrs. Clinton certainly has her own problems trying to herd Democrats into her corner. But just when it seemed that the Democratic Party was close to anointing Mr. Obama as its nominee, he lost yet again in a big general election state, dragged down by his weakness among blue-collar voters, older voters and white voters. The composition of Mrs. Clinton’s support — or, looked at another way, the makeup of voters who have proved reluctant to embrace Mr. Obama — has Democrats wondering, if not worrying, about what role race may be playing.“I’m sure there is some of that,” said David Axelrod, Mr. Obama’s senior political adviser, as he considered how race was playing among voters in late primary states. Mr. Axelrod said Mrs. Clinton’s biggest advantage had been among older voters, “and I think there is a general inclination on the part of the older voters to vote for what is more familiar.” He added: “Here’s a guy named Barack Obama, an African-American guy, relatively new. That’s a lot of change.” SOURCE: NYTIMES