Half the Republican base believes the unsecured border and the 10s of millions in the illegal population constitute an existential crisis whereby elections are at risk of being fraudulent. This is a deeply complicated subject, as it's the reason McCain and Bush failed to pass their "comprehensive immigration reform" 12 years ago. The base revolted against them for not wanting to secure the border and deport people first and foremost. These voters are scared, and acting crazy as a result.
"Acting?"
I know... you don't really understand them but they're the sorts I come from. I know a great deal about what drives at least some of them. I say it's a complex issue because there are various interests united here. There's plain old racists, there's nationalists, there's refugees, there's the poor. People who have different reasons but come together under this... issue. They really think it's important and that the nation is lost without effective action.
Reagan promised to secure it, and lied to them. Bush Jr promised... and lied. Trump promised and... well it gets old saying it after a while. With each successive liar trying to favor this voting bloc and failing to actually do something meaningful for them... they grow more desperate. Also because a state like Alabama has gone from 1% to 10% Hispanic in just the past 17 years. These voters have lived long enough to see the demographic tidal wave. They blame this issue, they blame past leaders, and this causes a sense of urgency. They cling to Trump for a desperate chance to fix it.
Trump is President in good part because he was the one to call it out and rally this segment of voters. Combined with his economic message, this made him stand out in the Primary. Otherwise he never stood a chance... but the rational Republicans were splitting the rational voters. Trump collected the rest, undivided.
Anyways, I've come to accept that there will be no mass deportation without violence. That it's just plain immoral. And in the face of such complexities my answer is to try and assimilate, to slow down immigration, to calm people. It's not easy to calm these voters though, especially next time the economy falters and Trump hasn't solved the issue for them. I'm afraid that, until we resolve their economic anxiety they're simply too embroiled into thinking something of value is being "taken" from them as a result of these "invaders". It's a depressing situation.
America needs a President who, on the back of a New Deal, can speak clearly with a sense of conviction that the moral choice for America is to respect the people living here, no matter their status. That we have taken the necessary steps to reduce their pain, and secure the economy. That they must give back by welcoming their fellow Americans. It's a nice dream, the trouble is how to get from here to there.