I'm not a conservative. But as to the optics and who made the best impression, I'd say Newt Gingrich or Rick Santorum. Gingrich didn't back down from his controversial statements about forcing low-income kids to be janitors, and Santorum nailed Romney on his Super PAC spreading falsehoods about Santorum and felon voting rights.
I personally like Ron Paul's idea of a "golden rule" foreign policy. But due to the fact that I was not the intended audience for the debate, I couldn't say he won.