He doesn't know what his campaign staff is doing, and bears no responsibility for their conduct, or so says ABC:
"With all our problems, why is John McCain talking about the sixties, trying to link Barack Obama to radical Bill Ayers?," an announcer says.McCain knows what his drones are doing. Obviously, if McCain doesn't want them to carry a particular message, he can order them to stop. Ordering his proxies to smear Obama doesn't remove any of the responsibility from McCain.
The spot is incorrect in insinuating that John McCain himself has brought up Ayers - it is in fact McCain's campaign that has sought to use the Ayers association against Obama, and McCain spokesman Brian Rogers did so again upon learning about the ad.