Washington (CNN) On the eve of a critical week of foreign policy challenges, Donald Trump started his Sunday by retweeting an edited video of him hitting a golf ball into Hillary Clinton's back -- and her falling over from the impact.

That message -- a trollish attempt at humor with o vertones of violence against women -- went out to Trump's 38.5 million Twitter followers and turned a Sunday expected to be focused on the President's preparations for the United Nations General Assembly meetings this week into a now-familiar White House circus.

The simple fact is this: With every passing day, it becomes more and more clear that Trump not only will never act "presidential" but also seems to revel in taking the very word -- and concept -- and dragging it through the mud.

Trump has been fixated on the idea of "acting presidential" (or not) for some time.

"At the right time, I will be so presidential that you'll call me and you'll say, 'Donald, you have to stop that,'" Trump told Fox News personality Sean Hannity back in March 2016. The following month, in an interview on the "Today" show, Trump made a similar promise : "I will be so presidential, you will be so bored. You'll say, 'Can't he have a little more energy?'"

And, at times in the campaign, he would go a day or even a few days in which gave a speech entirely from a teleprompter or didn't personally attack another politician on Twitter or avoided savaging the reporters covering his campaign as some of the most dishonest people in the world.

But those periods were the exception, not the rule. Trump would always return to who he really is: a coarse provocateur -- happiest when he is in the midst of some spat or another. While he bills himself as a counterpuncher, Trump is more accurately understood as a street brawler: He looks for fights and, when he finds them, he does anything and everything to win. The only goal is survival.

Since winning the White House, Trump's promises of a presidential pivot have become fewer and farther between as he appears to have more fully embraced his Internet troll persona.

"My use of social media is not Presidential - it's MODERN DAY PRESIDENTIAL," Trump tweeted . "Make America Great Again!"

My use of social media is not Presidential - it's MODERN DAY PRESIDENTIAL. Make America Great Again! — Donald J. Trump (@realDonaldTrump) July 1, 2017

Polling in July by The Washington Post and ABC News suggested that "modern day presidential" wasn't working out all that well for Trump. Seven in 10 people in the poll said Trump's "behavior as president" was "unpresidential" as compared to 24% who described it as "fitting and proper." (Almost 4 in 10 Republicans -- 38% -- said that Trump had acted unpresidential since entering office.)

But what Trump is doing is about more than just what the poll numbers say. The impact of his behavior on our politics and our culture could be much more far-reaching and potentially damaging.

"Every one of us should be offended by the vindictive and candidly dangerous messages the president sends that demean not only Secretary Clinton, but all women," California Sen. Dianne Feinstein (D) said in a statement Monday afternoon. "Grow up and do your job."

Trump defines the word "presidential" negatively. For him, acting in a way consistent with the men who have held the nation's highest office before him is just a media construct. There's not really any such thing as "acting presidential" in Trump's world. If you're the president, you can act however you want because, well, you're the president. Might makes right. The president is presidential by default.

That view is consistent with this moment in our culture. The Kardashians have made being famous a goal in and of itself. It doesn't matter what you do with the fame. What matters is that you are famous. YouTube has convinced every person that theirs is a voice -- and a set of opinions -- that need to be heard. Twitter -- and social media more broadly -- rewards takedowns of people; the bigger the person (in terms of number of followers) you dunk on, the brighter your star theoretically shines.

But, the presidency -- until Trump -- was conceived of as being immune to (or at least above) those sort of lowest-common denominator instincts. From the day that George Washington decided he wouldn't seek a third term as our first president, there has been a "country first" mentality among our chief executives.

There was a sense of passed-down responsibility -- that, by dint of the position to which you were elected, you were required to try to always take the high road, to appeal to people's better angels rather than their lowest impulses. (Yes, I know Bill Clinton had an affair with a White House intern. And that other presidents have not exactly been angels either. With Trump, however, there appears to a goal of degrading the office in a way I've not seen from any past president.)

That sense that the office changes the man elected to it was what kept people who didn't vote for Trump hoping he might be different once he sat behind the Resolute Desk in the Oval Office.

With eight months of Trump's presidency in the rear-view mirror, that possibility seems both quaint and laughable. Trump seems focused on destroying the idea of "acting presidential," glorying in the gasps and he-tweeted-whats that now happen on a near-daily basis. He believes -- I guess? -- that in acting the opposite of how we have long believed presidents are supposed to act, he is affirming his everyman credentials and sticking up for the little guy in the unending war against the elites.

It's that same mentality that led sports radio personality Clay Travis -- in a live CNN interview about ESPN's Jemele Hill on Friday -- to say: " I believe in the First Amendment and boobs."

Travis, as his smirk made clear, believed he was being edgy and giving the middle finger to the political correctness police with his "take." He was sticking it to the liberal media! He was a hero of free speech!

But here's the thing: He wasn't any of those things. Travis was just being a bro. He was expressing a misogynistic sentiment in a totally inappropriate setting. Like, why does the subject of boobs come up in an interview about whether or not Hill should be allowed to refer to Trump as a white supremacist? That's like me shouting "boobs" in mid-air of a cross-country flight and congratulating myself for my bravery.

Opposing societal norms that are inherently unfair or misguided is one thing. Flouting conventions of good behavior (or, in Trump's case, presidential behavior) is something totally different.

Trump seems intent on defining the presidency downward. The question is whether the American people will follow him even further down.