A worker labors at a romaine lettuce farm outside San Luis, Arizona in this November 9, 2010 file photo. Millions of illegal immigrants are at the sharp end of a daily battle for survival on the margins of American society as Obama pushes for immigration reform in Washington, months after Hispanic voters turned out to give the Democrat a second term.REUTERS/Eric Thayer (UNITED STATESSOCIETY AGRICULTURE - Tags: SOCIETY IMMIGRATION AGRICULTURE POLITICS)