Trump's immigration "policies" get a lot of support because they basically mirror the same kind of simplistic truth people believe: Illegal immigrants have broken the law and should be deported, walling off the border between the US and Mexico will keep them out, lack of rigorous immigration enforcement enables illegal immigrant criminals to commit crime.
It seems easy to me to understand why people so easily believe in these ideas, they have a kind of uncomplicated truth to them. If you are not residing or working in the US legally, why shouldn't you be deported? Certainly a large wall on the border would greatly hinder illegal imimgrants from infilitrating the border. We certainly don't want people with violent criminal histories entering the US, bypassing immigration allows these people to enter the US and potentially commit crime and deporting illegal immigrants before they commit crimes seems to have a certain preventative logic to it.
Of course, none of these "positions" or "ideas" is more than surface deep. The basic logisticts of deporting all illegal immigrants is pretty crazy and lacks a certain humanity in many cases. It's debatable how effective some giant wall would be and who the hell would pay for it?
None of it seems to address deeper questions of the problems of the current immigration system or why both political parties seem willfully unable to address it, or the value their constituences see in the current system, from cheap, wage-suppressed labor or for political pandering to immigrant groups to expansion of presumably political friendly constituencies.
And all of them avoid the kind of hard debates on well, who should be allowed to assume residency and work in the US? Is someone going to actually step up to the plate and argue for an open borders policy in an honest an direct manner (it would appear that Trump is the advocate for the opposite policy)? If it's not open borders, then how, exactly will we regulate and enforce an immigration policy in a way that's consistent and achieves desirable goals?
What's always surprised me is the lack of African American voices in the immigration debate. They have the highest unemployment rates and illegals take the kind of low-skill, entry-level jobs one would assume that would be the easiest for the many African Americans with poor educations to take. This leads to the questions of racial discrimination, although that seems complicated by the idea that Latinos can get these jobs. Then there's arguments about jobs "we won't do" but this begs the quesiton as to why those jobs don't pay more (I guess they don't have to with a supply of illegals) or whether people have some moral right to not work for jobs they don't want, yet be able to demand subsidies for not working.