He did it by saying "anybody who says they want 0bama to fail is an idiot." Since Rush is the only one coming out front and center to say that, it's clear who he's talking about.
Sanford is one of those guys who rises up for some occasions (spending), but with this, (BS) global warming, and I'm sure other things, sinks back down just as quickly.
Notice that he did not say that anyone who THINKS that he wants Obama to fail is an idiot. Apparently, his only objection is to verbalizing it.