Pity the poor American voter.As if listening to all the mudslinging and the whining, the backpedaling and the obfuscating weren't bad enough, the electorate's eardrums are also under assault from that most grating of noises: the candidate trying to sing.And sing. And sing.It's President Obama's fault. Well, Mitt Romney's, too. Each shares some of the blame, although for different reasons. Romney because he insists on singing for audiences even though he sings really, really badly. Obama because he's paying for campaign ads that force voters to listen to Romney singing really, really badly.