How would such a fence play politically? Well, it's a horrible symbol, one that clashes with the welcome mat laid out by the Statue of Liberty in New York Harbor. More important, it says to Mexican-Americans: We don't want any more people like you coming into our country. Nope. Nope, and Nope.
The welcome mat was for legal immigrants. As far as I know, we still allow legal immigrants.
The fence is to stop the flood of illegal immigrants. The message is to come legally, or not at all, Not that we do not want Mexicans to come here, but that we want them to abide by our laws when they do. Coming here in violation of our laws shows contempt for our legal system and our country from the git-go.
The point is that mexicans and other hispanics dont care if youre trying to keep out illegals or both illegals and legals. They will vote for whoever brings in more of their countrymen.