Why did The Dead get cancelled at the DNC

I thought I heard that The Grateful Dead had their invitation yanked from the DNC. Does anybody know why this happened??

 

I was unaware of their involvement in the DNC. If indeed they were supposed to be there, my guess is that the Democratic party decided to alter the plan as their single greatest critism that they are facing is fielding a team that is too liberal. I don't agree with this assesment, but if you are concerned with appearing too liberal, then having The Dead play at an event would probably not be such a good idea.

 

Or it could be that they were already booked at the Tweeter Center in Boston, as well as at other venues across the nation.