This troubled me too for a while, but then I considered his character and his words and actions of the past year, I came to the conclusion that he cannot rubberstamp this bill.
The fact that he does indeed 'say what he means, and mean what he says,' as Dick Cheney has also voiced several times in the past few days, reassures me that he will do the right thing.
We may be guessing, but as others have stated, we've seen before that he was playing chess when his opponents were playing checkers. What matters here is that he's not guessing.