Why It's So Hard for Trump to Retreat on Immigration

Since launching his presidential candidacy 14 months ago, Donald Trump's most consistent and uncompromising policy issue has been immigration. Indeed, it was the subject of his first general-election TV ad that started airing on Friday. Yet over the weekend, his top aides and advisers suggested that Trump might be shifting on his past position that all of the 11 million undocumented immigrants living in the United States must be deported forcibly.