Mexico retained Barbour's services in 2001 in order to have him drum up support for the extension of a provision that allowed undocumented immigrants to apply for visas or green cards without having to return to their countries of origin for three-to-ten years. The provision expired in 2002.
Barbour still sounds like he supports comprehensive immigration reform, so it's not like he's done an about-face on this issue, but actually being a paid agent of a foreign nation attempting to subvert our American laws might not go over well with Tea Party voters. (Because they blame immigrants for everything that they don't blame ACORN for.)
Alex Pareene writes about politics for Salon and is the author of "The Rude Guide to Mitt." Email him at firstname.lastname@example.org and follow him on Twitter @pareene