I've heard from a number of sources that once Bush makes up his mind he never changes it. If true, the die is cast and it will be another 3 long years of misery. My personal opinion is that Bush, for whatever reason, wants the Mexican Invasion to continue and is not afraid of losing reelection because of it.
Just as during the criminal reign of the Clintons, Congress is our only hope in staying in the game until we can get that *unusual* president that puts the interests of America before self-interests or with Bush, foreign interests.