Other than jet fuel and some additional staff? Probably not a lot, by his standards. He gets at least $10 or 20 million dollars of free publicity a day and I might be low on that. Why buy ads at this point? Most world leaders other than Mr. Obama would love to have his visibility.
BINGO! He doesn't need to do anything but give his speeches, give his interviews, and let this happen on his behalf. Ironically, when Walker was "winning" talk radio, the internet, etc, HE was winning and getting millions a day in publicity too. This is the new Republican Primary...the Rush Drudge Breitbart primary. It's the ONLY way for a non estab to win the nomination, period.
The warning would be, if he says or does anything to run afoul of this group, it will hurt significantly. If Rush would but be a little more balanced, it would in fact IMO.