On Monday, though, Walker went even further, suggesting that even legal immigration might depress native-born workers' wages.
"In terms of legal immigration, how we need to approach that going forward is ... to make decisions about a legal immigration system that's based on, first and foremost, protecting American workers and American wages... what is this doing for American workers looking for jobs, what is this doing to wages, and we need to have that be at the forefront of our discussion going forward," Walker said.
His new stance is not only at odds with his past statements, but also with research on the economic effects of immigration and a few of long-time principles of his party. Republicans have typically argued that they want to stop illegal immigration and that they oppose amnesty for illegal immigrants, not that they want to limit legal immigration as well. A frustrated former aide called Walker's change in position a "full, Olympics-quality flip-flop."
A spokeswoman for the governor later attempted to clarify his remarks--though they still appear quite muddy. "Governor Walker supports American workers' wages and the U.S. economy and thinks both should be considered when crafting a policy for legal immigration," AshLee Strong told Talking Points Memo in statement for an article about senior GOP lawmakers' criticisms of Walker's remarks.
"He strongly supports legal immigration," Strong added.
Walker's evolution on the issue echoes that of Sen. Marco Rubio (R-Fla.), who has also walked back from his previous support for a comprehensive immigration overhaul. Rubio, though, has not gone so far as to indicate skepticism about legal immigration as well.
Walker's new position has support from Sen. Jeff Sessions (R-Ala.), another prominent member of the party on the Senate Judiciary Committee. In Monday's interview with former conservative television personality Glenn Beck, Walker cited a column Sessions authored in The Washington Post earlier this month.
In the column, Sessions calls for fewer immigrants to be allowed into the country legally. He writes that immigrants, including those who have arrived legally, are depressing wages for workers born in the United States, citing a paper by George Borjas, an economist at Harvard University. He also claims that legal immigrants are "mostly low-wage."
Both of these premises are questionable.
The effects of immigration on wages are debated, but Borjas's paper is an outlier among the many studies economists have conducted on the subject. As Wonkblog has reported previously, most of these studies have concluded that immigration has very little effect on wages. It might cause declines for blue-collar workers, but those losses are likely to be minimal.
Workers with limited skills may find themselves competing with immigrants for jobs and accepting lower wages as a result. At the same time, lower wages for unskilled labor means that businesses are more profitable, encouraging employers to create new positions for workers born in the United States who might have been out of work otherwise.
What's more, since 2007, more immigrants to the United States have been highly skilled than unskilled, according to the Brookings Institution. The financial crisis made work here harder to find, discouraging potential migrants without skills from making the trip.
Sessions is confronting opposition from a broad range of Republican constituencies. Those with libertarian inclinations, like Shikha Dalmia at Reason and Alex Nowrasteh the Cato Institute, argue that further limits on legal immigration would amount to a major governmental restriction on people's freedom to move, work and live where they like.
Another conventional goal of the Republican Party is protecting economic growth. While there is dispute on whether immigration reduces wages, particularly for blue-collar workers, there is general agreement that immigration improves economic growth on the whole.
Yet Sessions's views have popular support.
More Americans would like to reduce the level of immigration than increase it, according to a poll Gallup conducted last year.
It seems he's also won the ear of Walker, who seems to be considering a more restrictive approach to immigration than his chief rivals have advocated. Any disagreements between the governor and other presidential hopefuls will lend a more combative tone to the GOP presidential primary on the issue of immigration.
Correction: An earlier version of this post misidentified Republican Sen. Jeff Sessions's home state. He is from Alabama, not Oklahoma. This version has been corrected, and we regret the error.