You nailed it right on the money. With Hillary and Obama throwing dirt at each other, McCain needs to keep himself clean.
The NC GOP will run the ad anyway, and if there’s backlash, McCain can say “I asked them not to do it”. McCain wants to run against Hillary, Obama has too much of a fund raising machine.
While I disagree with McCain on a few issues, I disagree on every issue with Obama and Hillary. Vote McCain people. The alternate is disaster.