The choice, like most vice presidential selections, also was a way for Romney to say something bigger about the kind of campaign he hopes to run. In that sense, advisers say, Ryan was "Mitt's pick, completely."
"Stories talk about it being a bold choice," said one senior Romney adviser, who spoke on the condition of anonymity to talk about the decision. "To me, it was a confident choice. He was very confident in himself, in Paul Ryan, in the campaign and in the direction of the campaign he wanted to take."
You could see how someone speaking so openly and candidly would need to have their identity protected. What if the boss found out you were the one who blabbed to a reporter about how wise and confident the boss is?!
Balz, for his part, doesn't even pretend there's a reason to grant this source anonymity: "This person's identity must be kept secret in order for them to say nothing particularly newsworthy" does not seem to live up to the Post's stated policy on granting anonymity.