I agree with you. And the problem is that most of the candidates running are squishy on the border, the ones who aren't openly for amnesty have all spoken up for it at one time or another. There are only a couple of people on that stage who can be relied upon to actually secure the border. Out of seventeen, only maybe two. Cruz, and Trump. The rest have spoken for amnesty, though at the moment they are all suddenly against it. Even Jeb was pretending to be for securing the border, and we all know where he stands on that issue.
Trump has forced everyone to pretend to be against amnesty.
I use the analogy of Solidarity in Poland.
It was a very wide coalition of people with all kinds of different political viewpoints, who united for the common cause. Then once Poland was free again, everyone went back to their corners and started anew.