I disagree that McCain has lost Ohio by this incident. If Cunningham wanted to call Obama a 'hack' on his radio show, that was his business. This was McCain's rally, and Cunningham didn't need to trash talk Obama.
I went to a Pres. Bush rally in 2004 with Bush and McCain, and neither one trashed Kerry. All the speakers talked about the merits of Pres. Bush. It was fun, exciting, and made Bush look like a great and humble man on TV news that night.
I have read in the local papers that Cunningham did exactly what the McCain crowd asked of him.
There were witnesses.