Ad Hominem

Obama attempts to strike down at Romney's integrity rather than talking about the actual issue they were talking about which was talking about coal as an energy source. Obama used cheap comebacks to make Romney not credible in the presidential debate.

http://www.telegraph.co.uk/news/worldnews/us-election/9613880/US-presidential-debate-Barack-Oba
ma-attacks-Mitt-Romneys-integrity.html