[Roscoe]

No one could ever break one of those!

Arnold knows it would be politically damaging when he did so, so he won't take a pledge he knows he'll break.

[DaughterOfAnIwoJimaVet]

I don't think you have any reason to fear that, Roscoe.

The truth is, you'd call him a liar if he DID sign it. He might be the only one who is being honest and realistic - but he can't win with you, so there's no point in even batting this around.