According to labor expert Peter Cappelli from University of Pennsylvania’s Wharton School of Business, African-Americans will be those most hurt by the Senate immigration bill.
He argues that despite the hype about a labor shortage, it really doesn't exist for any but the highest level jobs as evidenced by the fact that wages for most jobs have failed to keep pace with inflation—something that's been obvious to alot of people for many years. If employers really were desperate for workers, they would have to pay more and offer better benefits to attract workers. Even the somewhat recent demand for construction workers was short-lived and merely showed up as a bubble that has long evaporated.
Cappelli says that by using immigrants, whether legal or illegal, to increase the number of workers vying for available jobs, the people most injured by the practice will be the "poor and uneducated" who will suffer depressed wages and low employment. African Americans are particularly vulnerable according to his research citing a study covering the years 1960 to 2000.
This explains why at least two big groups oppose the bill: African Americans and organized labor.