>> reporter: some of trump's day one promises have been broad and vague. >> on my first day, we're going to immediately terminate every single unconstitutional executive order signed by president obama. >> reporter: the big question is what trump will do about one of the most controversial obama executive actions, allowing undocumented immigrants who came to the united states as children to stay. republicans have talked tough about reversing that but actually doing it and potentially allowing millions of people to be deported could be quite different. >> we're back with dana bash and jeffrey lord and julia cayenne, national security analyst, author of "security mom." dana, you're hearing about a particular executive order on immigration. >> that's right. what the piece ended with, the question about what he's going to do about here in washington, they call it daca and the real world, it means the people who came here as children, president obama signed an executive order