I think it is too late, the public has associated open borders with the GOP, and since Bush is aggressively pushing another illegal give away, the GOP's goose will be cooked in 2008. Also add to that bigger and bigger trade deficits, bigger and bigger budget deficits one might come to the conclusion that the GOP is unable to govern the country. I have voted GOP all my life, but I am about to give up on them. The current GOP policies on trade, jobs, immigration, and the role of the Federal government are insane.
"I think it is too late"
It's not too late. The 2008 primary will be crowded with RINOs (McCain, Romney, Giuliani, Hagel). If the social conservatives and law-and-order conservatives (anti-amnesty) can unite, they will win.
The key is to find a candidate with broad appeal, a strong resume, strong personal morals, and a commitment to border security and preservation of human life.
I don't think the public believes that liberal Dems will throw illegal immigrants out of the country.
I have a feeling the GOP nominee in 2008 is going to be someone who is not being talked about today.