Acting White House chief of staff Mick Mulvaney was unable Sunday to come up with the name of a single former president among those who told Donald Trump they support the border wall — as the president has claimed they have.

Mulvaney blamed Senate Minority Leader Chuck Schumer (D-N.Y.) for the apparent lie.

Trump said in comments outside the White House Friday: “This [wall] should have been done by all of the presidents that preceded me and they all know it. Some of them have told me that we should have done it.”

Asked by Jake Tapper on “State of the Union” Sunday to identify which presidents Trump was talking about, Mulvaney admitted, “I can’t name any.”

“My guess is that this boils down to some of the semantic difficulties with leader [Sen. Chuck] Schumer,” Mulvaney said before suddenly veering into an unrelated discussion of wall construction. (See the video above.)

“You don’t know what president it was then?” Tapper pressed again.

“I have no idea,” Mulvaney said. “I have not asked the president that question.”

Trump doubled down on the issue Sunday in a tweet indicating that “Barrack” Obama backed the wall. Trump quoted Obama as saying that “we cannot allow people into the United States undocumented” — which says nothing about a border wall.

Mulvaney was also challenged about Trump’s bizarre claim from last week that the Soviet Union (from which Russia emerged) invaded Afghanistan in 1979 in response to terrorist attacks on the communist state (and that the people of Afghanistan were happy about it). Mulvaney again was unable to support the president’s statement.

“I think those are comments the president made born out of frustration from where we are and I’m not too concerned about the details,” Mulvaney responded.

That led ProPublica reporter Peter Elkind to quip on Twitter that it’s a good thing an official who doesn’t sweat the details is no longer the head of the Office of Management and Budget. The joke is that Mulvaney is still the head of the OMB, a post he will continue to hold while he is also acting chief of staff.

“Not too concerned about the details”? Glad Mulvaney’s no longer running the Office of Management and Budget! https://t.co/LV2RxV4uLb — Peter Elkind (@peterelkind) January 6, 2019

The Wall Street Journal in an editorial that first appeared Friday blasted Trump’s tale about the Russian invasion of Afghanistan as the most “absurd misstatement of history by an American president” in memory and bashed his claim that the invasion was justified as “absurd” and “reprehensible.”

Despite the grilling he got in the Tapper interview, Mulvaney chirped that being the acting chief of staff is “actually a lot of fun.”