As President, Bill Clinton popularized the 'Third Way', which was one of the incarnations of triangulating against one's own base and the opposition. The Third Way, when successfully executed, yields a healthy percentage of the moderate middle, while alienating only a small percentage of the hard-core base, which will still likely vote along party lines.
Long story short; in failing to deal effectively with the Mexico problem, President Bush is pioneering the Fourth Way, in which an attempted appeasement of the middle will fail to yield any of the moderate vote, while radicalizing the base to the extent that they do not vote, or even protest in disgust by voting for another candidate.
Even President Reagan could not leap this chasm in two short hops--the 1986 amnesty was one of his few unmitigated failures. Bush is a fool to try.
This Fourth Way is the mirror reflection of the Third Way; halfway between the two ends of the political spectrum, but rather than elevated in success, sunken in failure.