I assume that you are asking why Cain cannot move Romney to the right?
The only real reason is that Romney underestimates Cain and over estimates himself. It’ a matter of Romney’s ego, not the fault of either Cain or Bachman.
I simply sense that Romney seems to fear Gingrich and maybe even Santorum, a bit. With Santorum, I think that Romney fears his core values, backed by intelligence. With Gingrich, I think that Romney purely fears his intellect, which is probably superior to any in this primary race.
I truly believe that conservative Republicans would be worse off with Romney in the White House, than Obama. I’m afraid that Romney would lead the RINO Republicans to vote as liberals and all we would get is Obama-lite.
My point is Romney has no core values. He’ll “move” whichever direction is politically expedient to him at the moment. He’ll screw you in the end every time.