What Donald Trump is doing and saying as a presidential candidate is not who we are as a country, says The Post's Jonathan Capehart. (Tom LeGro/The Washington Post)

“Defining deviancy down.” That was the provocative title of a 1993 essay on crime written by the late Sen. Daniel Patrick Moynihan (D-N.Y.). He explained his concept succinctly a few months later at a breakfast of civic-minded New York City movers and shakers. “I wrote that there is always a certain amount of deviancy in a society,” Moynihan told the Association for a Better New York. “But when you get too much, you begin to think that it’s not really that bad. Pretty soon you become accustomed to very destructive behavior.”

Again, Moynihan was talking about the tolerance of crime. But as the 2016 Republican presidential contest drags on, his diagnosis fit politics in general and the campaign of Donald Trump in particular. Just when you thought the Big Apple billionaire couldn’t sink any lower, he does. He gleefully dances through the nativist, racist, misogynistic slop as if he were Gene Kelly  in “Singing in the Rain.” And to make matters worse, Trump is rewarded for it.

[“Cheryl, what do you think a Trump presidency would look like?” Cheryl said, “Like classy.”]

Trump launched his campaign in June saying, “When Mexico sends its people, they are not sending their best. … They are sending people that have lots of problems,” he said. “They’re rapists. And some, I assume, are good people.” He retweeted and then deleted a contemptible comment from a follower in July who wrote, “@realDonaldTrump #JebBush has to like the Mexican illegals because of his wife.”

By the middle of July, Trump aimed his rhetorical flame thrower at Sen. John McCain (R-Ariz.). “He’s not a war hero,” Trump said at an Iowa event with pollster Frank Luntz, who challenged that assertion. “He’s a war hero because he was captured. I like people that weren’t captured, OK?” I was among the many who thought Trump’s nascent presidential campaign was over. How wrong we all were. The ensuing controversy only served to make him stronger.

During the first GOP debate, Fox News’s Megyn Kelly listed a slew of nasty adjectives he’s used about women. “Only Rosie O’Donnell,” Trump said to applause and laughter. He expressed his displeasure with Kelly asking the question by telling CNN, “You could see there was blood coming out of her eyes, blood coming out of her wherever. In my opinion, she was off base.” His Twitter tirade against Kelly was outright bullying.

In a Rolling Stone profile Trumped opined on fellow Republican candidate Carly Fiorina’s face.

Look at that face!” he cries. “Would anyone vote for that? Can you imagine that, the face of our next president?!” The laughter grows halting and faint behind him. “I mean, she’s a woman, and I’m not s’posedta say bad things, but really, folks, come on. Are we serious?”  

Fiorina’s response to Trump in the September debate was pitch perfect. “I think women all over this country heard very clearly what Mr. Trump said.” I believe it was the answer that won her that debate. But the boomlet of attention for the California Republican dissipated quickly. Trump remains top of the heap.  

[Trump v. Carson: Bad luck or merely terrifying?]

When it looked like Trump was losing his front-runner status to Ben Carson, the billionaire builder used a 95-minute campaign “speech” this month to tear into the famed neurosurgeon. Trump was unsparing in his view of  Carson’s explanation of his youthful violent past as being the result of having “a pathological temper – a disease.” He likened it to child molestation. “[I]f you’re a child molester, there’s no cure,” Trump said, “They can’t stop you. Pathological, there’s no cure.” That speech also featured Trump cursing.

The jaw-dropping horror of the Trump campaign dropped even lower over the weekend. At a rally in Alabama on Saturday, he repeated the widely debunked conspiracy theory that thousands of Muslims in New Jersey cheered as the World Trade Center crumbled to the ground on Sept. 11, 2001. He defended the falsehood on ABC’s “This Week with George Stephanopoulos” on Sunday.

[What Omarosa gets right about Trump and why that’s horrifying]

It was at that same Alabama rally that Trump had an African American protester shouting “Black Lives Matter” ejected from the arena. That man — Mercutio Southall Jr. — said and video shows him being assaulted by Trump’s supporters. The candidate’s response? “Maybe he should have been roughed up because it was absolutely disgusting what he was doing.” You’ll recall that it was also in Alabama in August that a man repeatedly yelled  “white power” during a Trump rally.

After defending his Sept. 11 falsehoods yesterday, Trump tweeted out a chart with crime statistics that were flat-out wrong.

No, 81 percent of whites were not killed by blacks. As Kevin Drum of Mother Jones points out, the latest FBI data show that “82 percent of whites were killed by other whites and only 15 percent were killed by blacks.” Perpetuating the racist perception and lie that marauding gangs of African Americans are killing whites is beyond repugnant. But we shouldn’t be surprised.

[Here’s what’s wrong with Trump’s deportation plan]

Trump is the man who said in the wake of the Paris terrorist attacks that he supported a registry of all Muslims in the United States. He said we have “absolutely no choice” but to close down some mosques. He advocates deporting all 11 million undocumented immigrants in the country. And he wants to deport their American-born children and repeal birthright citizenship.

After all this, Trump still leads in the polls. No amount of condemnation of his divisive, racist rhetoric seems to halt his advance. What he is doing, what he is saying is not who we are as a country. What he is doing and saying is not just “defining deviancy down,” it’s destroying our country.

Follow Jonathan on Twitter: @Capehartj