For Jeb Bush this is a two-fer. The trans-national corporatists want cheap labor. And for Jeb, this is a family issue. His wife’s father was an illegal alien. He married a Mexican, who has barely assimilated.
His brother took his marching orders on immigration policy from Vincente Fox, who at the time was basically demanding that the US take up Mexico's entire surplus population and keep the remittances coming. Jeb would be even worse as a US President, but on the upside, he'd make a great President for Mexico. The only question is whether he should run as PRI or PAN.