Many will say Trump won because he successfully capitalized on blue collar workers' anxieties about immigration and globalization. Others will say he won because America rejected a deeply unpopular alternative. Still others will say the country is simply racist to its core.

But there's another major piece of the puzzle, and it would be a profound mistake to overlook it. Overlooking it was largely the problem, in the first place.

Trump won because of a cultural issue that flies under the radar and remains stubbornly difficult to define, but is nevertheless hugely important to a great number of Americans: political correctness.

More specifically, Trump won because he convinced a great number of Americans that he would destroy political correctness.

I have tried to call attention to this issue for years. I have warned that political correctness actually is a problem on college campuses, where the far-left has gained institutional power and used it to punish people for saying or thinking the wrong thing. And ever since Donald Trump became a serious threat to win the GOP presidential primaries, I have warned that a lot of people, both on campus and off it, were furious about political-correctness-run-amok—so furious that they would give power to any man who stood in opposition to it.

I have watched this play out on campus after campus. I have watched dissident student groups invite Milo Yiannopoulos to speak—not because they particularly agree with his views, but because he denounces censorship and undermines political correctness. I have watched students cheer his theatrics, his insulting behavior, and his narcissism solely because the enforcers of campus goodthink are outraged by it. It's not about his ideas, or policies. It's not even about him. It's about vengeance for social oppression.

Trump has done to America what Yiannopoulos did to campus. This is a view Yiannopoulos shares. When I spoke with him about Trump's success months ago, he told me, "Nobody votes for Trump or likes Trump on the basis of policy positions. That's a misunderstanding of what the Trump phenomenon is."

He described Trump as "an icon of irreverent resistance to political correctness." Correctly, I might add.

What is political correctness? It's notoriously hard to define. I recently appeared on a panel with CNN's Sally Kohn, who described political correctness as being polite and having good manners. That's fine—it can mean different things to different people. I like manners. I like being polite. That's not what I'm talking about.

The segment of the electorate who flocked to Trump because he positioned himself as "an icon of irreverent resistance to political correctness" think it means this: smug, entitled, elitist, privileged leftists jumping down the throats of ordinary folks who aren't up-to-date on the latest requirements of progressive society.

Example: A lot of people think there are only two genders—boy and girl. Maybe they're wrong. Maybe they should change that view. Maybe it's insensitive to the trans community. Maybe it even flies in the face of modern social psychology. But people think it. Political correctness is the social force that holds them in contempt for that, or punishes them outright.

If you're a leftist reading this, you probably think that's stupid. You probably can't understand why someone would get so bent out of shape about being told their words are hurtful. You probably think it's not a big deal and these people need to get over themselves. Who's the delicate snowflake now, huh? you're probably thinking. I'm telling you: your failure to acknowledge this miscalculation and adjust your approach has delivered the country to Trump.

There's a related problem: the boy-who-cried-wolf situation. I was happy to see a few liberals, like Bill Maher, owning up to it. Maher admitted during a recent show that he was wrong to treat George Bush, Mitt Romney, and John McCain like they were apocalyptic threats to the nation: it robbed him of the ability to treat Trump more seriously. The left said McCain was a racist supported by racists, it said Romney was a racist supported by racists, but when an actually racist Republican came along—and racists cheered him—it had lost its ability to credibly make that accusation.

This is akin to the political-correctness-run-amok problem: both are examples of the left's horrible over-reach during the Obama years. The leftist drive to enforce a progressive social vision was relentless, and it happened too fast. I don't say this because I'm opposed to that vision—like most members of the under-30 crowd, I have no problem with gender neutral pronouns—I say this because it inspired a backlash that gave us Trump.

My liberal critics rolled their eyes when I complained about political correctness. I hope they see things a little more clearly now. The left sorted everyone into identity groups and then told the people in the poorly-educated-white-male identity group that that's the only bad one. It mocked the members of this group mercilessly. It punished them for not being woke enough. It called them racists. It said their video games were sexist. It deployed Lena Dunham to tell them how horrible they were. Lena Dunham!

I warned that political-correctness-run-amok and liberal overreach would lead to a counter-revolution if unchecked. That counter-revolution just happened.

There is a cost to depriving people of the freedom (in both the legal and social senses) to speak their mind. The presidency just went to the guy whose main qualification, according to his supporters, is that he isn't afraid to speak his.