It would probably help your case if you were to cite a few specific examples.
The two things I can remember are (1) he was a major player in the Colossal Medicare Prescription Drug Giveaway, and (2) a couple years ago, he killed the Senate Energy Bill when he found a way to attach to it $50M+ for his idiotic Iowa Child Project indoor rain forest "tourist attraction" a.k.a. "The Pork Forest." (He eventually got the $50M by burying it in an omnibus appropriations bill; unlike energy bills, appropriations bills are immortal).
Please remind me of some other examples. I must admit I tend to forget bad memories.
He sold out to the moderates on the Bush Tax Cut, channeled the ghost of Karl Marx and said that the oil companies should share the wealth, endorsed Ganske over Salier, blatantly lied about the medicare costs, voted to federalize airline security, voted for the Department of Homeland Security, introduced legislation to allow illegal immigrants access to American universities, voted for the Highway bill...