Trump has shown little respect for traditional behavior or concern about the horror that erupted when people he would describe as elites learned about his words in a Washington Post report.
Yet the remark still has the power to shock because it upends conventional expectations about the dignity of the presidency itself and the mystique that frames the chief executive as the upholder of national morality and diversity.
It also appears to run counter to the idea that traditional presidents repeatedly invoke: that the American dream does not discriminate on the basis of race or origin but hinges on an individual's character, industry and willingness to embrace a set of national values traced to the enlightenment.
"I think we all collectively should be a little bit frightened. That is the President of the United States, and he is not appealing to the better angels of our nature or our nation's values," former CIA and National Security Agency chief Michael Hayden told CNN's Erin Burnett.
CNN political analyst David Gergen said Trump's message was "if you are not white, you are not welcome. We have never had that message before."
Perhaps sensing the political ramifications of his explosive remark, Trump denied Friday morning that he made the comment, saying that although his language at the meeting was tough, "this was not the language used."
Despite the denial, Trump's reported remark is hardly a departure, since the comment, in a meeting Thursday with lawmakers debating a Capitol Hill immigration bill, comes from racist rhetoric and imagery fundamental to his political project from the start.
In the same meeting, he said, "Why do we need more Haitians? Take them out," a source told CNN's Jim Acosta.
Little respect for tradition
Trump's contempt for convention was also in evidence in a unchained interview with the President that The Wall Street Journal published Thursday and in a Twitter intervention about a House of Representatives debate on the surveillance powers of US spy agencies that sparked chaos and confusion and questions about Trump's command of the issue.
Such episodes revive the debate about the President's temperament and coherence, which the White House has been trying to squelch in the wake of a stunning fly-on-the-wall book written by Michael Wolff.
At one point, in the Journal interview, Trump appeared to indicate that he had already had spoken to Kim Jong Un, saying he "probably" had a good relationship with the North Korean leader, and he accused an FBI agent, who was dismissed from Robert Mueller's Russia probe for attacking him in a text message, of treason.
In fact, the wild day at the White House showing the impulsive and prejudiced sides of his character probably more accurately reflects who Trump really is than the staged, reality show-style meeting on immigration he convened Tuesday.
Proof lies in the fact that the White House did not react to Trump's "shithole" comments with panic or any sense that he had detonated a damaging gaffe that could cause him lasting political damage.
A White House statement by spokesman Raj Shah read more like a defense and a justification of the President's comment, portraying it as the sentiments of a man who was fighting for the Americans who are already here.
"Certain Washington politicians choose to fight for foreign countries, but President Trump will always fight for the American people," Shah said. "The President will only accept an immigration deal that adequately addresses the visa lottery system and chain migration -- two programs that hurt our economy and allow terrorists into our country."
Another White House official, speaking on condition of anonymity to CNN's Kaitlan Collins, was even less apologetic, saying his sentiments would likely help Trump with his loyal voting base, much like his attacks on NFL players who took a knee to protest police brutality and racial discrimination earlier this season.
By now it's clear that Trump uses ethnic nationalism and racist rhetoric as a political tool, and that he is playing into a well of prejudice he sees among the grass roots against immigrants with dark skin.
When he launched his presidential campaign, he referred to Mexicans as "rapists," and last year he said there were good people on "both sides" of clashes between neo-Nazis and protesters in Charlottesville.
He was reported as saying by The New York Times in December that all Haitians have AIDS and Nigerians live in "huts." His comment Thursday that he wanted to welcome more Norwegian -- i.e. white -- immigrants was along the same lines.
Outrage spilled quickly
A cynic might argue that the President, who may be on the verge of doing a deal with Democrats to permit hundreds of thousands of undocumented immigrants brought to the US as children to stay, finds himself at a political moment when he needs to protect his populist credibility with his voters.
Outrage spilled quickly across party lines Thursday as Washington learned about Trump's remarks.
Republican Rep. Mia Love of Utah, the first Haitian American elected to Congress, said the comments were "unkind, divisive, elitist and fly in the face of our nation's values" and called on the President to "apologize to both the American people and the nations he so wantonly maligned."
Democratic Rep. Luis Gutiérrez of Illinois said he was ashamed of Trump: "We can now say with 100% confidence that the President is a racist who does not share the values enshrined in our Constitution or Declaration of Independence."'
Whenever Trump triggers outrage, and crashes through the behavioral constraints and decorum of the presidency, there is a sense that he has hit a low, or has gone too far and will finally pay a sharp political price.
But one advantage of basing his presidency on a narrow political base rather than reaching out in an effort to unify the nation is that the wounds he can inflict to his own standing are limited.
Trump's willingness to use politically incorrect language and slurs was key to his appeal to a certain section of the electorate in 2016, and those voters are unlikely to change their views over his remarks on immigrants.
But while Trump's base will remain robust, Thursday's developments will provoke new questions about the state of his mood, and whether he possess the character, knowledge and leadership skills expected of a president.
One White House official expressed surprise to CNN's Jim Acosta that the President would make such a remark in a meeting with lawmakers, given that it was likely to get out.
His comments on North Korea also mystified Washington -- since if he had spoken to Kim, it would mark the first time a sitting US president had ever talked to a North Korean leader.
"I probably have a very good relationship with Kim Jong Un of North Korea," Trump said. "I have relationships with people, I think you people are surprised."
Asked by a Wall Street Journal reporter to clarify whether he had spoken with Kim, he replied: "I don't want to comment, I'm not saying I have or I haven't."