At the start of his meeting with Democratic congressional leaders this week, Donald Trump repeated one of his favorite lies. “Tremendous amounts of wall have already been built,” the president said, referring to his border project.

He added, “A lot of wall has been built. We don’t talk about that, but we might as well start, because it’s building – it’s being built right now, big sections of wall.”

We’ve heard nearly identical rhetoric from Trump countless times in recent months, despite the fact that it’s demonstrably ridiculous. Congress approved funding for border-security measures, including resources to replace old fencing, but lawmakers haven’t approved a penny of the president’s plan to build a giant wall along the U.S./Mexico border.

Given the absurdity of our current political circumstances, when the president lies like this, it hardly seems notable. Trump has told this lie before, he’ll tell it again, and there’s no longer much of a point to making a fuss about it.

Yesterday, however, the Department of Homeland Security published a new memo, insisting that the Trump administration is, in fact, building a border wall. The headline on the DHS piece was, simply, “Walls Work.”

DHS is committed to building wall and building wall quickly. We are not replacing short, outdated and ineffective wall with similar wall. Instead, under this President we are building a wall that is 30-feet high. FACT: Prior to President Trump taking office, we have never built wall that high. Once funding was provided, DHS began construction of border wall exceptionally quickly….

Look, I think reasonable, objective observers can agree that Trump’s credibility evaporated quite a while ago. Much of the country realizes that the president has a strained relationship with reality, and his boasts are generally seen through that lens.

But Americans still need to have some confidence in the Department of Homeland Security, so when it peddles Trump’s fiction as if it were fact, it’s undermining the credibility of an agency we’re supposed to be able to trust in the event of an emergency.

I realize some officials like to play some rhetorical games about the meaning of the word “wall,” but as NBC News explained again yesterday, “The government is currently repairing and replacing old sections of border fencing, but construction on a new section of border barrier has not yet begun and won’t this year.”

As for the idea that repaired fencing should be seen as evidence of “the wall,” the NBC News report added that Trump “repeatedly derided fencing on the 2016 campaign trail in favor of a concrete barrier that would run the 2,000 mile stretch of the U.S.-Mexico border.”

It’s a safe bet the Department of Homeland Security knows all of this. It makes yesterday’s deceptive memo that much more problematic.