So Trump is all but certain to be the Republic presidential nominee this year. Why is that? He's an outsider, obviously, but that doesn't explain it completely. Ben Carson and Carly Fiorina were also outsiders, as have been Herman Cain and Steve Forbes in the past. Trump is more willing to be blunt and offensive than any of these, but I don't think voters are just looking for someone who violates social norms.
What does Trump stand for, in a positive sense? What particular policies has he advocated? You could, no doubt, list quite a number of issues where Trump has weighed in, but I doubt the average person would be aware of most of them. Nor would these issues distinguish Trump from the rest of the Republican candidates, even in aggregate. He has propounded chiefly conservative views, very incoherently at times, but not views much different from Cruz, Rubio, or any of the other candidates.
I found that I could name exactly one specific policy that I knew Trump stood for, and I'll bet it's the same one you and most other Americans know: building a wall to keep illiegal immigrants out. I have a strong suspicion that this stance, more than any other, has propelled Trump's success. The majority of Americans may or may not be for stopping illegal immigration; I suspect most are, but many are embarrassed to admit it for fear of appearing racist or mean. But I am pretty sure that there is a large section of the country that is very committed to stopping illegal immigration, and these people are tired of the country's continual failure to do something about it.
In addition to building a wall, you probably also know that Trump has promised to make Mexico pay for it. This seems unlikely to actually happen, but I think this second aspect of his immigration policy is central to Trump's appeal. It's not that people care about the money, which I have seen estimated at $8 billion. We spend that much on the military every few days, and only slightly less on things like unemployment, welfare, and medicare. The more expensive aircraft carriers cost nearly as much. If you asked people if they would be willing to forego one aircraft carrier for the price of a wall, I have no doubt that at least 80% would agree.
It's not the monetary savings that makes this such an important part of Trump's message, but the signal that he is serious about it. For one thing, politicians bicker about money all the time. How are we going to pay for this massive expense? Trump has made it front and center that he is not going to pay for it, the Mexicans will. That forecloses one major potential barrier -- perhaps the major barrier once Trump is president -- immediately. It also makes the wall, and Mexico's payment for it, Trump's one unique contribution to public policy. It is not one idea in the midst of many that he might back out of, but rather his central plank. "Trump" means "a wall on the border." If he doesn't push that as hard as he can, he will end up looking like...
Well, what? George Bush when he promised no new taxes? Barack Obama when he said he would close Guantanamo Bay? Marco Rubio when he said repeatedly that he opposed amnesty for illegal immigrants? Politicians are politicians, and when they get in office they often find the perspective is quite a bit different from the outside. Things that seemed desirable and practical before suddenly look like insurmountable obstacles. They want to be popular, not the person who rammed a policy through to fulfill a campaign promise that only a portion of their constituency cares about. In short: flip-flopping is, I'm afraid, endemic to the profession of politics, both those who make a career of it and those who serve Cincinnatus-like terms when their country needs them.
Nevertheless, Trump sounds more credible on this issue than any of the alternatives. No Democrat that I am aware of supports enforcing immigration law, but even Republicans have been tainted with dithering and compromise to the point that no one believes that they will do anything about the issue. None of the existing candidates, that is. As an outsider who has made illegal immigration the centerpoint of his campaign, Trump seems the most credible alternative to voters who care about this issue, and there are more than a lot of people want to admit.