I'm no expert on the law here, but if I understand correctly, no one in a candidate's campaign is permitted to have any dealings with a PAC--and vice-versa.
You obviously don’t remember the way that George Bush and John McCain handled the Swift Boaters, do you? They did everything they could to let the public know that they considered the Swift Boaters to be the enemy, damn Karl Rove to hell.
Campaign Finance Reform law says a PAC can’t say, “Vote against socialists like Scott Brown.” But it can say, “Tell Scott Brown you reject his socialist policies.” Therefore, I’m sure that while a candidate can’t say, “RomneyPAC, quit digging up dirt on Herman Cain,” he absolutely can say, “I find it appalling that Republican PACs are digging up sexual accusations against Republican competitors, and I find it all the more infuriating that some of these are even doing it in my name, and that campaign finance reform says I can’t tell them to stop it.”
It's called the First Amendment and it applies to candidates.
It's called the First Amendment and it applies to candidates.