Washington is locked in a destructive and acrimonious ritual that plays out every time President Donald Trump is called upon to lead in a moment of national peril -- and that ensures that America's political estrangement will only deepen.
The controversy over explosive devices sent to prominent Democrats, a liberal billionaire and CNN -- all frequent targets of the President's rhetoric -- is following a pattern repeated over and over during over 21 tumultuous months.
When a natural disaster, a political controversy or a mass shooting takes place, the media and political establishment set expectations for Trump to invoke a poetic vision of common purpose and unity, craving a spectacle in line with the traditional conventions of the presidency at great historical moments.
Trump then produces a scripted response that is adequate, but in the moment or in subsequent days undercuts that message with radioactive comments or tweets that spark fierce criticism and mobilize the conservative media machine in his defense.
It suggests the President has little desire to play the role of national counselor being forced upon him -- one that is a poor fit given his deliberately divisive style. The drama usually ends with another layer of bile added to the nation's politics.
That a President who has based his political career on crushing conventions and norms should so constantly be tripped up by the behavioral and ceremonial codes that define the role of head of state is deeply ironic.
But his situation also helps explain why the political divides and mutual mistrust cleaving America -- between Trump loyalists and critics -- are unbridgeable and will produce a bitter 2020 election campaign.
The last few days have stuck to the script.
Undermining his own words
As soon as authorities discovered that homemade bombs had been sent to former President Barack Obama and the home of former President Bill Clinton and former Secretary of State Hillary Clinton, as well as other Trump targets like George Soros and CNN, eyes started turning to the White House.
The President had to say something, and he did so at the top of a previously scheduled event on Wednesday.
"I just want to tell you that, in these times, we have to unify. We have to come together, and send one very clear, strong, unmistakable message that acts or threats of political violence of any kind have no place in the United States of America," Trump said, slamming the "egregious" and "abhorrent" attacks.
It was a strong statement on the face of it, though was notable in failing to name any of the victims, all often the focus of Trump's ire.
But Trump got a passing grade in the eyes of most commentators.
It was only later that his unwillingness to play the role presidential tradition requires became clear. At a rally in Wisconsin, the President undercut his message by appearing to blame the media and his opponents for the sour national mood in which the pipe bombs had been crafted and delivered.
His performance not only flouted the paternal conventions of the modern presidency -- which date at least to Franklin Roosevelt's fireside chats during the Great Depression -- it also suggested that when he's not in a formal, scripted setting, Trump really cares only about his own political motivations.
"It was one of the worst moments in the Trump presidency," said CNN presidential historian Douglas Brinkley. "It was a golden opportunity to be large, to try to say something that would unify the country. ... He came off, in my opinion, as a very small president."
The President's attitude set off a media storm, and then a backlash from his White House. Press secretary Sarah Sanders accused reporters of always focusing "on the negative" and not playing their own role to foster national unity.
Trump next fired off a tweet unleashing new acrimony, sparking fresh accusations about his attitude toward norms and constitutional freedoms and his understanding of what a president is supposed to do.
The fight back on such occasions resonates with Trump supporters, however, who see the President as the victim of unrelenting and slanted news coverage, a factor that endears him to them even more.
One Trump confidant told CNN's Jeff Zeleny that criticism of the President's behavior over the bomb scares just cemented Trump's view that he is "treated with hostility and unfairly -- there's no talking him out of that."
This was not the first time that the criticism of him left Trump brooding after critics charged that his performance fell well short of the standards of decorum and decency expected of a commander-in-chief and revealed a leader unable to rise above political combat to console and steer his nation.
After violence at a white supremacists rally in Charlottesville, Virginia, last year in which an anti-racism protester was killed, Trump was initially criticized for an inadequate response but then delivered a speech condemning an "egregious display of bigotry, hatred and violence" that has "no place in America."
But he couldn't help himself. A day later in a Trump Tower news conference, he blamed "both sides" for the violence, setting off a days-long debate about race.
"You had a group on one side that was bad. You had a group on the other side that was also very violent. Nobody wants to say that. I'll say it right now," Trump said.
It was almost as if the President couldn't let his scripted, "presidential"-style remarks have the last word. Maybe it's a symptom of his rebellious character. Or perhaps it shows a need to signal his loyal base, which embraced his revolt against the establishment, that he hasn't gone native in Washington.
The same scenario unfolded when Trump returned from Finland amid outrage over his deference to Russian President Vladimir Putin at a summit.
He read out a statement designed to make clear he accepted intelligence community assessments on Moscow's interference in the 2016 US election. But he couldn't resist adding a caveat -- "could be other people also" -- in an ad-lib that undermined his statement but was also an act of defiance against Washington's expectations.
Every time the weight of convention and tradition requires him to act one way, Trump the outsider and iconoclast can't bring himself to comply.
And each time, the criticism that Trump stirs, and consequent fury within his inner circle at the media response, makes the polarization even worse.
It's been a trait of his presidency right from the beginning, emerging when he went to the CIA on his first full day in office, attacked the media for its coverage of his inaugural crowds and effectively conducted a campaign rally in front of the agency's revered memorial wall to fallen officers.
Gravity of the presidency
Some commentators believe Trump simply has no desire to honor the moral authority of the presidency and simply sees it as a vehicle for his own power, prestige and self-glorification.
Others suggest he doesn't understand the magnitude of his responsibilities.
"He is now the President of the United States. He is not on a talk show somewhere," New York Gov. Andrew Cuomo told CNN's Brooke Baldwin on Thursday.
"When that position of power is spewing hateful rhetoric, that has an effect."
Another theory about Trump's behavior could be that he has banked so exclusively on his political base that he cannot allow himself to do anything that would damage his image as the ultimate rabble-rouser.
The President also knows he's most effective when he's attacking an enemy, in the heat of a fight. And a political method that relies on inflaming cultural, racial and societal divides means he might not ever be accepted by those who despise him anyway.
But that all leaves a bigger question: What will be the impact on American life and national unity of years of such civic discord?
Trump may simply be unable to summon the words and the aspiration to bring the country together -- as President George W. Bush did on a pile of rubble after 9/11 -- or he may not even want to do so.
Ultimately, as a self-styled disruptor, he may realize that it's simply impossible to honor the historical expectations and conventions of his job while being true to himself. And if it comes to a choice, there's no doubt which side of that equation he will choose.