Senator Harry Reid (D-NV), the Senate majority leader, has become famous for making wild charges and insisting everyone accept them as if they were real. In his world, it's "guilty till proven innocent."
Then there's the issue of why Reid is doing this. And why President Barack Obama and his Whihte House and his Administration and his campaign have all refused to disavow Reid's fantasies. It makes me think they put him up to it.
These both seem to be related to Reid's fantasy charge that Romney hasn't paid any taxes in ten years. (That's a hard charge to support, given that Romney has released his 2010 return and most of his developing 2011 return both of which show he paid taxes.)