Obama's extraordinary denunciation of the presumptive Republican presidential nominee was about far more than a personal intervention on behalf of Hillary Clinton in the ugly general election campaign.
The commander in chief's fury, which seethed out of him in a stunning soliloquy on live television, amounted to a moment of historic significance: a president castigating one of the two people who could succeed him as beyond the constitutional and political norms of the nation itself.
Obama's remarks, motivated by his disgust over Trump's response to the worst terror attack since 9/11, were also deeply ironic, given that Trump has hounded him for years with insinuations that he's not a real American.
The real estate mogul had returned to that theme on Monday, hinting that in some way the President was complicit or approved of Islamic terror attacks, saying on Fox News, "There is something going on."
Trump has based his attacks on conspiracy theories that Obama was born outside the country or a closeted Muslim. Obama's charge, in contrast, was based on his perception that the billionaire Republican's views are so extreme that he threatens the fabric of America itself.
And Obama sought to shame Republican leaders, many of whom were left squirming by Trump's views. Though they differ with many of his views -- House Speaker Paul Ryan again on Tuesday rejected the GOP presumptive nominee's stance on Muslims -- they are trapped by his millions of primary voters, who made it clear to the party leadership that the billionaire businessman should be heeded.
"That's not the America we want," he said. "It doesn't reflect our democratic ideals. It will make us less safe."
Obama also drew an implicit analogy between Trump's call for a ban on Muslim travel and the most "shameful" moments in American history when the government had mistreated its people, adding that then Constitution prohibited religious tests.
"If we ever abandon those values, we would not only make it a lot easier to radicalize people here and around the world, but we would have betrayed the very things we are trying to protect," Obama warned.
Trump responded to the President during his Thursday night rally in Greensboro, North Carolina, saying Obama "was more angry at me than he was at the shooter."
"The level of anger, that's the kind of anger that he should have for the shooter and these killers that shouldn't be here," Trump added, blasting Obama as a "lousy president" who had done a "terrible job."
Obama has pilloried Trump before. But Tuesday's remarks displayed a deeper intensity and anger, reflecting his apparent belief that America had reached a dangerous moment given Trump;s new status as the presumptive Republican presidential nominee.
"I think the key for President Obama -- is he is talking to the world," presidential historian Douglas Brinkley told CNN's Anderson Cooper. "Donald Trump isn't just a candidate who a few months back was talking about banning Muslims from the United States. He has got a lot of momentum."
He continued, "President Obama wanted to make clear that the United States government, the federal government says no to what Donald Trump is suggesting, that it is hateful bigotry."
He concluded, "There was ire in his eyes and sarcasm in the way he went after Trump."
Obama told his aides on Monday that he wanted to deliver a speech rebutting the Republican nominee's comments after stewing over them, a senior administration official told CNN's Dana Bash.
The result was the kind of public venting that Obama, one of the world's most self-contained politicians, rarely indulges in publicly -- though this side of his character is familiar to those who have witnessed the much more impassioned rhetoric he adopts in private.
In some ways, it recalled the angry tirade against American politics that Obama delivered after the Newtown massacre of defenseless schoolchildren in 2012 and the subsequent rant he delivered about politicians that he implied were too cowardly to embrace his crusade for gun control.
He hammered Trump over his "dangerous" mindset and "loose talk and sloppiness" about who exactly America was fighting, implying that Trump's remarks were actually driving Muslims who might be prone to radicalization into the arms of ISIS.
And he doubled down to repudiate Republican campaigns that he was abetting terrorism by refusing to use the words "radical Islamic terrorism."
"What exactly would using this label accomplish? What exactly would it change?" Obama asked during remarks at the Treasury Department. "Would it make ISIL less committed to try and kill Americans?" he continued, using a different acronym for ISIS.
"Would it bring in more allies? Is there a military strategy that is served by this? The answer is none of the above," he said. "Calling a threat by a different name does not make it go away."
Speaking after Obama's remarks, White House Press Secretary Josh Earnest said the President had grown frustrated at hearing "political talking points" being wielded in place of a comprehensive counterterrorism strategy.
But while the President's remarks likely cheered many of his supporters, the tone of his comments -- which included a call for gun control -- contained little reassurance for Americans scared about a new wave of homegrown terror on U.S. soil.
And while Obama mounted a stern defense of his administration's battle to eradicate ISIS in its self-declared caliphate in parts of Syria and Iraq, his remarks will not assuage critics who argue he was late to the fight and is still not doing enough.
Mike Rogers, former head of the House Intelligence Committee, faulted Obama for treading the same kind of political terrain as Trump with his angry remarks.
"This was the chance for the President to try to bring us together. I think he is so focused on this presidential campaign he let himself go," Rogers, now a CNN commentator, said on "The Lead" with Jake Tapper. "I just don't think it looked presidential."
Obama's intervention also seemed motivated by a desire to help Clinton.
The former secretary of state lit into Trump herself on Tuesday, warning that Trump was temperamentally unfit to serve in the Oval Office.
She also made the case that his obsession with the words "radical Islam" was a smokescreen for his own lack of knowledge.
"Is Donald Trump suggesting that there are magic words that once uttered will stop terrorists from coming after us?" Clinton said in Pittsburgh. "What I will not do is demonize and declare war on an entire religion."
The Republican Party did lash out at Obama, however, with RNC Chairman Reince Priebus hitting out at the administration's record on fighting terrorism and faulting Clinton and Obama for pushing for gun control in the wake of the tragedy in Florida.
"Let's not forget: President Obama's hasty and politically driven withdrawal from Iraq, which Hillary Clinton supported, created the vacuum that enabled the rise of this terrorist group," Priebus said in a statement.
"Their failure to secure Libya after their military intervention gave ISIS a beachhead on another continent. Democrats want to talk about anything else because they have lost the national security debate."