WASHINGTON -- Republicans often rail about undocumented immigrants. But Wisconsin Gov. Scott Walker, an expected GOP presidential candidate, took it a step further Monday by sounding some critical notes about the number of those who immigrate to the U.S. legally. "In terms of legal immigration, how we need to approach that going forward is saying -- the next president and the next Congress need to make decisions about a legal immigration system that’s based on, first and foremost, on protecting American workers and American wages.