FILE - This May 5, 2012 file photo shows former astronaut and former Ohio Sen. John Glenn speaking before a campaign rally for President Barack Obama at The Ohio State University in Col

 

              FILE - This May 5, 2012 file photo shows former astronaut and former Ohio Sen. John Glenn speaking before a campaign rally for President Barack Obama at The Ohio State University in Col
FILE - This May 5, 2012 file photo shows former astronaut and former Ohio Sen. John Glenn speaking before a campaign rally for President Barack Obama at The Ohio State University in Columbus, Ohio. Whatever their political beliefs, some artists perform an age-old ritual: warming up the crowd before a political rally, generating enthusiasm and all-important buzz for events that otherwise could be overlooked in a crowded news cycle. For politicians _ even those as well known as Obama and Republican presidential candidate, former Massachusetts Gov. Mitt Romney _ celebrity warm-up acts can provide validation by taking them out of the political realm into popular culture, said Darrell West, director of governance studies at the Brookings Institution think tank in Washington. (AP Photo/Mark Duncan, File)