In January 2016, Donald Trump said something unintentionally profound: “I could stand in the middle of Fifth Avenue and shoot somebody, and I wouldn’t lose any voters.” We’ll hopefully never find out whether Trump really could get away with murder. But we now know he can at least falsely accuse someone of murder without triggering a political exodus.

This “Fifth Avenue problem” is a central puzzle of the Trump presidency. Somehow, Trump can tweet something that would destroy any other politician when he wakes up, and it’s forgotten by lunchtime.

Don’t believe me? In the last week, Trump didn’t just make a false accusation of murder. He also praised one of the United States’ most virulent anti-Semites as a man who bestowed “good bloodlines” on his descendants. He retweeted a man who called Hillary Clinton, the first woman to be a major-party candidate for president, a “skank.” Trump shared an image with Nancy Pelosi, the first woman to serve as House speaker, with duct tape over her mouth and then mocked her physical appearance. And he repeatedly fabricated lies about voter fraud.

If Joe Biden behaved like that, it would destroy his career. But when Trump does it, it has no significant impact on his support. His depravity is now just widely assumed. It’s baked in.

That presents a paradox: The last three years have felt like we’re collectively strapped into the world’s worst roller coaster — of endless scandals, tweets in search of reality and new lows for presidential conduct. Yet for all those disorienting twists and turns,and the seemingly endless plunge of presidential standards, Trump’s approval rating has remained pretty much the same.

In functioning democracies, politicians live and die by public opinion. George W. Bush certainly learned that lesson. After 9/11, his approval rating soared to 90 percent. As the Iraq War worsened and the economy collapsed, he hit a low of 25 percent. Nearly 7 out of 10 Americans changed their minds about him at some point during his presidency.

Trump is fundamentally different. According to Gallup, his highest approval rating has been 49 percent; his lowest, 35 percent. For 103 out of the 130 polls Gallup has conducted since Trump took office, his approval rating has been stuck between 37 percent and 43 percent. (The margin of error is usually around 3 percent, so it’s plausible that public opinion rarely moves and we’re mostly seeing statistical noise.)

Heck, during the pandemic 100,000 Americans have died and nearly 40 million Americans have become unemployed. And still Trump’s approval rating has moved up and down a few percentage points at most. How is that possible?

There are three main reasons for this “Fifth Avenue problem.”

First, Trump gets away with it because the previously unthinkable has become routine. As a species, we are drawn to fresh and surprising information — something we could call “novelty bias.” What would surprise you more: Trump amplifying a lunatic conspiracy theory in a tweet or him unequivocally praising the sacrifices of immigrant nurses and doctors during the pandemic? The former happens all the time; the latter would provoke breathless commentary. Is Trump finally making his mythical pivot to being presidential? Is this a new general election strategy? For every other mainstream politician, that dynamic would be inverted.

That’s why this week’s Sunday morning shows focused on Joe Biden’s recent bungled joke (for which he quickly apologized). Meanwhile, Trump’s praise of a well-known anti-Semite and his false accusation of murder weren’t mentioned.

Second, it’s not easy for humans to admit when we are wrong. It produces a feeling called cognitive dissonance. That has always been true. But for Trump voters, who have, by now, stuck with him despite him boasting about sexual assault, countless scandals and a steady stream of racism, the psychological cost of breaking ranks has soared. His supporters would have to say to themselves: “All of Trump’s previous conduct was acceptable, but this is the final straw!” There is a ratcheting effect. The more you were willing to accept, the harder it is to let go.

Third, U.S. politics is now defined by a phenomenon called “motivated reasoning,” the tendency to see reality through the lens of desired outcomes. For many Trump voters, reality stretches to fit a prior worldview. Every Trump scandal proves that the “deep state” exists. Every new revelation about Trump’s unfitness for office proves that he’s the victim of “fake news.” Everything in our politics is filtered through the prism of pro-Trump/anti-Trump divides. We’ve reached the dystopian moment in our politics in which taking common-sense actions to stop the spread of a virus by wearing a mask is a partisan act.

None of this is to say that Trump can get away with everything. He is losing support among key demographics during the pandemic, most notably with the crucial voting bloc of Americans 65 and older. In a competitive election, even modest changes can spell doom for a candidate.

But let’s be frank: American democracy is badly broken if few people change their minds about a president who falsely accuses someone of murder or boasts about his TV ratings while 100,000 Americans lose their lives and nearly 40 million lose their jobs. And that says as much about the dysfunctional state of our country as it does about Trump.

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Democratic Party strategist and lawyer Marc Elias says that flaws in ballot design are often overlooked but have huge repercussions on elections. (The Washington Post)

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