He has a likability issue and came off as defensive and a bit angry.
He spun that he has a history of defeating incumbent Democrats but ignored the huge loss in his most recent election. I didn't get the sense he's over that defeat.
I'm inclined to seek alternatives rather than trading one jerk from the Senate for another. Temperament matters.
You are right about Santorum. He could not even carry his home state of Pennsylvania. All his shenanigans in Pittsburg make for effective opposition ads.
And for flip-flopping, he would make Romney blush.