!!!! Are you serious? When and where has Romney gone after Obama? He is on record saying he will NOT go after him. Romney keeps talking about how Obama is a nice guy, just out of his league, and one of his Stepford sons said he likes Obama. Mitt won't even call Hussein a socialist. So, I don't know, I must have missed all the pit-bull attacks.....
http://news.yahoo.com/video/politics-15749652/romney-attacks-obama-in-portsmouth-visit-29139363.html
http://www.govexec.com/management/2012/04/romney-attacks-obama-over-gsa-scandal-new-web-ad/55471/
Come on, that was a simple Bing search.