If he wants to take a bus he can take a bus. The problem here is he is turning a campaign event into an official trip in order not to have to pay the bill.
Do you have any idea why POTUS always travels in Air Force One? It gives him access to the best com equipment the DOD can get its grubby paws on. In order for him to take a bus tour, and still be able to handle an emergency, someone is going to have to design a bus that can handle all the communications duties of the single most secure mobile communications system on the planet. That is not going to be free, nor is it all going to fit in one bus. There will also have to be three complete shifts of people to monitor that equipment traveling with him, which will take more buses. It would actually be less expensive to fly the plane overhead and give him an uplink to it than to build a completely new system that will only be used once, and is intended only to prove that Obama is something everyone knows he isn't.
The bus was purchased by the Secret Service for exactly this purpose. Before this they had to retrofit rented out buses. So it's actually cheaper now, then it was before.
You missed the entire point I was trying to make.
The Secret Service never purchased a bus before because no president has traveled by bus in years. The Secret Service retrofitted buses to protect candidates, which requires a lot less technology than protecting a president.
My point wasn't even about the Army One bus, it was about the fact that there has to be an entire mobile communication system that follows the president around when he travels, that is why they use the plane. That center will also have to designed and purchased, and it will only be used once, because no other president will ever be arrogant enough to think that anyone will believe he is going on a bus tour because he is just like them.