From what I can tell, many Trump supporters are single-issue voters. Their primary issue is illegal immigration.
That is, indeed, a massive problem, including welfare, identity theft, voter fraud, street gangs, public education, prison population, ER closings, &c.
This is a bipartisan failure. Traditionally, Democrat officials pander to this constituency for votes while Republican officials pander to this constituency for cheap labor.
However, judicial meddling is what gave illegal immigrants a foothold. In 1982, the Supreme Court (in Plyler v. Doe) concocted a new Constitutional right requiring American wage-earners to educate the children of illegal immigrants. Likewise, Federal judges struck down California Proposition 187.
Not surprisingly, many voters are incensed by how the power elite has circumvented the democratic process. In addition, there's the sense of injustice: if you cheat, and you hold out for long enough, the political establishment will eventually reward cheaters.
However, solutions are harder to come by. How can a national (i.e. presidential) candidate win by taking a hardline on illegal immigration? Problem is, he needs enough electoral college votes to win. To do that, he must pick up some key states in the SE and SW. Yet those regions are illegal immigrant strongholds. Between the political map and electoral college math, he's caught in a vice.
At this stage, the best strategy might be to run on a Federalist plank with respect to immigration. Leave it up to the states to formulate their own policies. States that pander to illegal immigrants will become death spiral states while states taking a harder line will prosper. Businesses will flee death spiral states, accelerating the death spiral. Sometimes a social experiment must be allowed to fail to demonstrate how that policy was, indeed, a dismal failure.
To make this work, Congress would have to pass a law limiting the subject-matter jurisdiction of the courts with respect to immigration. Congress has that general prerogative. It should be possible for a presidential candidate to run and win on Federalism–among other issues. And depending on the particular state, it's possible for politicians for local or statewide office to win while taking a hardline on illegal immigration. From what I can see, that's the best bet.