To appease Latin America before they slip over to the other side. (Chavez's demented ass)
"To appease Latin America before they slip over to the other side. (Chavez's demented ass)"
That's more or less it. There's a strong marxist movement in Mexico playing 'populist' against the quite real corruption there.
Right now the primary force holding Mexico together is the huge influx of $ sent home by Mexican immigrants, both legal and illegal. Without that $ there's a serious possibility that Mexico could collapse and a marxist Chavez type take over. This would obviously be Very Bad; you can imagine the trouble if Al-Q types were not merely able to cross through unconcern on the part of Mexico, but actively funded, sheltered, and abetted by a marxist Mexican government.
Personally I think we ought to seal the border and let the chips fall, with the intention of helping Mexico reform, if it collapses, in a less corrupt and not marxist shape. I think that's a better long-term intention than propping up Mexico as-is. But, I thought it'd be helpful to point out that at least a sizable chunk of our policies toward Mexico are not driven by domestic economics. That tends to get lost in the shuffle.