Case in point, Bush meeting with homosexuals during the 2000 campaign. Now despite our gravely oversexed society, there just aren't enough activist homosexuals in the world to justify Bush spending any time at all with them to get their votes.
But Bush spent time with them to send a message to the voters in the mushy middle: I, George W. Bush, am open-minded. I am not a bigot. I care about all Americans. You can vote for me and not be worried that you will be embarrassed in front of your wine and cheese intellectual friends.
Having said that, I still believe that Mexican immigrants will vote Democrat, and I can't think of any constituency group that will be more likely to vote for Bush because of this. The socialists will vote Democrat regardless, because a Republican will never outspend a Democrat. Hispanics, blacks, welfare recepients: ditto Democrat.