Trump portrays a world in which crime is skyrocketing (it isn't) and illegal immigration is skyrocketing (it isn't) and skyrocketing immigration explains skyrocketing crime (it doesn't, because neither of those things is happening). He says he can build a 1,600-mile wall across the southern border at a reasonable cost (he can't), and he says he will get Mexico to pay for its construction (he can't). He says immigrants are depressing average Americans' wages (they aren't) and that Hillary Clinton has a plan for open borders (she doesn't).
Trump is, on some level, surely aware that he is bulls---ing. He worked in the real estate development industry and knows better than you or I do that the logistical requirements to undertake the wall project as he's defined it are mind-boggling. At times, he's even considered owning up to that fact.
Portions of the US-Mexico border, for example, run through roadless, uninhabited desert. To build a wall there, you would need to build roads to transport the material, build places for the workers to live, hire other workers to maintain the colony, and somehow pay everyone enough to make it worth their while to go live in a temporary camp in an uninhabited desert. It's self-evidently absurd, and of course Mexico isn't going to pay for it.
Trump is Trumps
Trump's passion, however, isn't for the details of border security or immigration economics. It's for lurid tales of bloodshed. He opened the speech with long descriptions of a handful of people who've been murdered by illegal immigrants, and he closed it with testimonials from relatives of the deceased. Lurid fantasies about avenging these crime victims have dominated much of Trump's "thinking" about politics ever since he made a splash with paid newspaper ads urging the execution of five young men who turned out to have been falsely accused of murder.
A normal person would feel ashamed to have once loudly and publicly advocating for the killing of five people for a crime they didn't commit. Not Trump. "These young men do not exactly have the pasts of angels," he wrote at the time. (Trump has bragged about punching his music teacher, which I guess is what angels do.) The one hint of moderation is that he said we should deport Hillary Clinton for unspecified crimes, which is much more restrained than earlier calls to have her locked up or maybe killed.
Trump is a person, not a cartoon. He can do a calm, controlled speech or even a calm, controlled week. But there is no calm, controlled, responsible version of Donald Trump the politician who can mount a sustained presidential campaign or who could serve for a sustained period of time in the Oval Office. As a political figure, Trump has always been a race-baiting, fearmongering demagogue and that's not going to change. If that's what you're looking for in a president, then you'll love the Trump administration. If you find it off-putting but you're really into tax cuts, he'll probably throw you those too.
But it's long past time to stop expecting someone to pull off the Trump mask and find some kind of earnest, responsible politician lurking underneath. The Trump we saw Wednesday night is the Trump who accepted the Republican nomination six weeks ago is the Trump who descended the Trump Tower escalators in Manhattan a year ago.
Trump is Trump.