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Donald Trump's insult comic routine is so familiar by now, it's easy to miss the subtleties that distinguish one slur from another. (Yes, I used "Trump" and "subtleties" in the same sentence.) Even so, some combination of pure native canniness and twisted psyche have combined in the GOP nominee to form an almost unerring sense for the exact right epithet for each target and each occasion. Perfect pitch for dog whistles is his superpower.

"Crooked Hillary," his most frequent riff, is the apex of the form. Superficially, this insult calls back to the appearance of untrustworthiness that Hillary Clinton has both fed and been burdened by for decades. The suggestion that Clinton's competence is actually Lady Macbeth–level scheming — that her abilities are inherently malevolent — goes back to Whitewater. But in Trump's dainty hands, paired with his overt accusations of "cheating" and a "rigged" election, what was once just a suggestion of misogyny has become a full-throated roar (or, given the petulant tenor of Trump's speeches, a full-on tantrum). In the context of his accusations of voter fraud, "Crooked Hillary" isn't just an insult on the level of "Lyin' Ted" or "Low-Energy Jeb" — it's something more akin to Trump's birtherism and obsession with President Obama's college transcripts. It's an attempt to completely delegitimize both Clinton and the entire system through which she's earned her success.

"Earned her success" is the primary problematic notion for Trump and his fans, though who knows how recent the vintage is on his resentment. Back when the earth was young and he wasn't running against her for president, Trump himself acknowledged — as almost any rational observer must — that Clinton is a highly accomplished public servant. We may never know whether his contempt is genuine and has always been festering under the surface or whether it's part of his carny-barker populist act, the result of his savantlike skill in tapping into and echoing the basest emotions and fears of a crowd.

We know that "Crooked Hillary" isn't really about favor trading or ties to Wall Street; if Trump actually cared about such behavior, he'd probably not go around bragging about his ability to buy politicians, or stack his economic adviser team with hedge fund managers and billionaires. If he were actually concerned about Clinton's ties to Vladimir Putin, he wouldn't tout his cheerful intent to "be friendly with" him. People wonder how Trump can sustain the cognitive dissonance inherent in calling out Clinton for the exact same behavior he flaunts. The answer is simple: It's different for girls. Trump's true objection isn't that Clinton's corrupt, it's that she's successful.

If you firmly believe that women are lesser beings than men, a woman's success isn't evidence that you're wrong, it's evidence that she cheated. Trump is the time-traveler from the past presented with modern technology; why, it must be witchcraft. The metaphor's not too far afield from a deeper truth: Trump is a kind of time-traveler from the past, one for whom the political advances of the modern era are too strange and unsettling to explain with anything but conspiracy theories and hocus-pocus.

That's the illogic that produced birtherism. Trump and the rest of those who still believe there's some birth certificate ruse can more easily imagine a massive, multi-generational conspiracy than they can believe that the nation's first black president arrived at the White House purely on his own merits, playing by the rules like everyone else. It's a form of denial: OK, Obama may be president, but it's not like he got it fair and square. There's fraud at the heart of his identity; he tricked us; if we had only known the truth ...

After all, "Crooked Hillary" is a kind of birtherism, too: She's just as disqualified to be president, because she was born a girl.