In a speech Thursday, the Philippines leader slammed EU ambassadors for allegedly criticizing his war against drugs, and told them they had 24 hours to leave Manila. That deadline is now up.
"You think that we are a bunch of morons here? You are the one. Now, the ambassadors of those countries -- if they are listening now -- tell me because we can have the diplomatic channels cut tomorrow. You leave my country in 24 hours. All! All of you," Duterte said.
"You idiots came to our land, Indonesia, Malaysia...the British and the Philippines for the Americans and Spaniards and you have the gall to say to us, we will expel you... Why? Because we are angry at you for colonizing and stealing our resources for so many hundreds of years."
While the focus of his ire this time was the EU, he had incorrectly identified the source of the criticisms.
The rebuke had actually come from the International Delegates of the Progressive Alliance, which had warned, when it visited the country in early October, that the Philippines may lose its EU Generalized Scheme of Preference (GPS) status if the killings continue.
The EU said the International Delegates of the Progressive Alliance was not an EU mission, saying the statements made by the alliance "do not represent the position of the European Union."
The Presidential Palace issued a statement, asserting that the alliance had "falsely portrayed itself as (an) EU mission."
"Any group or person who unduly interferes in our domestic affairs demeans our status as a sovereign nation. For as long as this condition remains, the President is duty-bound to preserve the integrity of the State," the statement reads.
One analyst, Richard Heydarian, an academic and political analyst who is the author of "The rise of Duterte: A populist revolt against elite democracy," told CNN that he thought the rant was "a knee-jerk reaction, not a final policy."
Was the outburst the result of a politician cornered?
The rant came just days after a Philippine survey company, Social Weather Stations (SWS), released an approval poll which suggested that the President had a an approval rate of just 48% -- the first time his popularity has dipped below 50% during his 16-month presidency.
Julkipli Wadi, former dean and professor at the University of the Philippines' Institute of Islamic Studies, says that for the Duterte presidency, "the honeymoon period has ended."
"The Malacanang (presidential palace) has felt the pressure from human rights group and the opposition about the EJK," he said, referring to the acronym for "extrajudicial killings," the widely used terminology for drug killings committed by police or vigilantes.
The premier's ratings have been dropping as the public tires of the bloody and seemingly intractable war on drugs, Wadi says. "Many people are really (angry)," calling the changing mood a "critical factor in the slide of Duterte's rating."
Street protests, especially in the wake of the killing of innocent teenager Kian Delos Santos
in August, have begun to turn the tide against the previously well-supported campaign.
"Kian was a turning point... this put the population into fear that their children could be killed," Wadi told CNN by phone.
"People began to question the whole war on drugs."
The turning of the tide of public opinion has left Duterte isolated and irritable, Heydarian said.
"These things struck a raw nerve. Even before the (SWS poll) came out, he gave some incendiary rhetoric, lashed out," Herydarian told CNN.
"He has been quite edgy, on the precipice of self-implosion."
Another factor which is affecting Duterte's popularity is the protracted siege of the Mindanao city of Marawi by ISIS-linked militants, analysts say.
Duterte was caught wrong-footed -- and indeed, overseas -- when the Maute group of Islamist militants stormed the city in May, causing huge displacement of civilians.
Pockets of militants are still holed up in the city, holding hostages, and the military has time and again moved back projected dates for retaking it.
The presence of extremists holding significant territory is a bloody nose for the president. Not only does Duterte need to "end the crisis," says Wadi, but also "to continue to address continuing radicalization.
In addition, the "rehabilitation of the city will be a test case," for Duterte's leadership, he says.
While his popularity is down, Heydarian doesn't think that the Duterte administration is in a death spiral.
"Historically speaking, people like (former president Ninoy) Aquino faced major crises in their presidency where their numbers tumbled but the numbers recovered," he said, reasoning that in the face of growing opposition to the war on drugs, Duterte is trying to right the course.
He's attempting this in part by switching the focus of arrests from street-level dealers to bigger players, and most notably, by turning over control of drug crimes to the Philippines Drug Enforcement Agency (PDEA) rather than local police forces.
"The president is looking at certain recalibrations, (he's) suspending 'tokhang,' to focus on high value targets," Heydarian said, referring to the controversial door-to-door searches that the police have been carrying out.
But, much like a previous attempt to suspend police from the war on drugs, which soon collapsed, Heydarian says that he doesn't think "it's a permanent change but a Machiavellian calculation" to boost Duterte's approval ratings.
As a populist leader who has often delighted voters with his nonconformist attitude and unvarnished approach, could the EU slanging be an attempt to divert attention away from his diminishing popularity?
"In the early days, maybe last year that kind of antic would increase his popularity and would entice more people to support him but this past month his comments, even his officials, have been (angered)," says Wadi.
"The firebrand antics are probably not gaining much popular support these days."
However, the academic concedes that, if a new election were held tomorrow, Duterte would probably win comfortably, largely due to the lack of a credible challenger.
"(Voters) are beginning to know the real persona of the president ... They're becoming increasingly critical. But there's still no alternative."