Why would he desire to lay his reputation on the line to lie for a liberal?
My guess? Sabato was a student-government geek at UVA and probably is still jealous of the handsome quarterback George Allen. Revenge of the Nerds, so to speak. Old grudges die hard. He just couldn't help himself. Hate held over for 30+ years can do that to you.
If that is the case, i.e. Revenge of the Nerds, then that would make Larry more of a self-serving liberal than a conservative any day!