So much for neutrality.

After insisting for months that he'd stay out of the Democratic presidential campaign until after Pennsylvania votes on April 22, Sen. Bob Casey Jr., endorsed Barack Obama today in Pittsburgh. That could help Obama make up ground with white, working-class voters in Casey's northeastern stronghold in Scranton and around the state. (In most states, the heavily Catholic, socially conservative bloc would be known as "Reagan Democrats," but here they're "Casey Democrats" after Casey's father, the former governor.) Polls show Hillary Clinton ahead by double digits.

"We know what this campaign is about," Casey told a rally here, introducing Obama as he kicked off a six-day bus tour of the state. "This campaign is a chance for America ... to chart a new course, to go down a different path, a path -- first of all -- of change. A path of a new kind of politics. And finally, a path of hope and healing. I believe in my heart that there's one person who's uniquely qualified to lead us in that direction, and that is Barack Obama."

Casey's family has feuded with the Clintons for years. Former Gov. Bob Casey, the senator's father, was blocked from speaking at the 1992 Democratic convention, where Bill Clinton was nominated for president, because of his antiabortion views (and because he hadn't yet endorsed the Clinton-Gore ticket). But Casey had said just a few weeks ago that "endorsements by superdelegates are vastly overrated," and that he'd wait until the primary here to make his choice public.

So what changed his mind? "For a long, long time I was not only neutral but an undecided voter," he told reporters after the rally. "This wasn't a process where [we] were talking back and forth and we were being lobbied. I had a couple days off with my family and made a very personal decision."

No matter what the reason, Obama was grateful. "I understood that wer're behind in Pennsylvania," he said at the rally. "It would have been easy for Bob just to stay out of it, to stay neutral ... When he called me and said, 'I just think this is the right thing to do,' it meant as much to me as any endorsement that I've received on this campaign trail, because I knew it was coming from the heart. I knew it wasn't coming from political calculation."

Casey will hop on Obama's bus for a campaign swing through western Pennsylvania.