He’s moved the Overton Window quite a bit. No one was willing to say deport before!
The window can still be moved a little more.
Now, as for deportations: there are two simple facts here. First, he is the ONLY candidate talking, on a regular basis, about deportations. (Key being "on a regular basis"). That alone is a very significant move of the "Overton Window." Second, except for the few, and I'm using the word generously, unrealistic types, you cannot deport either 11 million or 30 million people.
The good news is you do not have to and I think this is what Trump is getting at. We do not have to arrest or cite every speeder in order to maintain speed limit laws. When it's clear you will be cited and, if multiple offenses, arrested, and you have cops who do this visiblly and frequently, everyone else complies with the law. I do indeed believe that if we deported even a million of Trump's "bad guys" and criminals, a very signficant number of the others would leave on their own before getting caught. It would never be 11 million---too many are established, like, for example, Cesar Milan, the "dog whisperer" who has a TV show and has been here all his life.
But many, many of those on the bubble, newly arrived, would go, particularly if you similarly inspect and enforce it at the employment end, too.
The key is that the system is horribly broken, even for the legal immigrants, and that we need to get as close to ground zero before we can start again. Trump, of all the candidates, seems to have this in mind.