In an Iowa interview with Roger Simon, Fred Thompson, promises to fight the good fight to keep the Republican Party principled and conservative.

Fred Thompson has a folksy, good old boy persona on the stump, but it may not last much longer.

When I asked him if he is an 11th Commandment man — Never speak ill of a fellow Republican — he responded, “I am more of a 12th Commandment man: Don’t speak ill of them until they speak ill of me. And then really speak ill of them.”

Thompson’s stump speech contains the warning that Republicans must “stay with our principles” when it comes to choosing a nominee.

I asked him if that was a veiled reference to Rudy Giuliani.

Thompson made a face of mock horror and laughed.