1) They have 'run the numbers' and looked at past RINO sellouts, and believe that in taking up the mantle of gradual regularization and legitimization of illegal aliens, they will gain access to Hispanic votes in 2004 and be assured of reelection;
and
2), they have concluded they would take a short term 'hit' from this from GOP conservatives in forums and on talk shows and at the grassroots and in Congress, but that after time all would settle down and the peristalsyic prospect of "President Hillary" or "President Gore" with no true conservative third party vote would be enough to keep them also in the 2004 column.
So they have taken the risk.
This is Karl Rove and others thinking and Bush carrying it out with full knowledge and forethought. Don't let anyone tell you that this is not happening. The real victim is the Republican who supported Bush and wants to support him again. It is very sad, pathetic and irritating to, as an American who believes in the rule of law and national security, be essentially taken for granted and treated in this rather shoddy way.