Bush didn't come up with this policy in a vaccuum. DeLay knew about it in advance, I'm sure. But DeLay is not afraid to come up with a different solution than the President, and getting this particular proposal through Congress is going to be tough.
The main concern I have is that there could be significant defections on the GOP side, meaning significant Democrats would have to support it in order for it to pass. That gives the Democrats the leverage to make it far more friendly to Mexicans than the President proposed.
It's still awfully early to handicap what will happen. There's no bill to look at yet.
I wish he would use his hammer on those who refuse to enforce current immigration laws.