Before we decide it won't work let's try it!
We did. 1953.
I'd much rather secure the border first and review the IRS information to pass-out felonies on all the illegals using false docoumentation. Then gives those individuals a free trip to Mexico. Clearly no-one can complain about doing this to people whom stole indentities...and sorry, you're not eligible for legal immigration, ever.
Bush is looking at the potential voter base these 20-30 million will add to the republican party. Remember, somewhere around 100 to 110 million voted in 2004 with the republican margin being only in the single digits.
Add another 20% loyal voters to that and elections are a lock.
I think he's a bastard for doing it.