Days before Donald Trump was elected president, then-Rep. Mick Mulvaney limited his endorsement of the Republican nominee. “Yes, I’m supporting Donald Trump,” he told a campaign debate audience. “I’m doing so as enthusiastically as I can, given the fact that I think he’s a terrible human being, but the choice on the other side is just as bad.” Two years later, Mulvaney would be acting chief of staff for that “terrible human being.” But though Mulvaney now evinces new enthusiasm for the president, he exhibits little to encourage anyone who hoped he might even briefly be a more responsible chief of staff.

On ABC’s “This Week,” host Jonathan Karl asked Mulvaney whether the president had broken his oft-repeated promise that Mexico would pay for the wall. Mulvaney first cited the new NAFTA-like trade deal, saying “you could make the argument that Mexico is paying for it in that fashion.” This, of course, is not how trade deals work. He also tried to cite Mexico keeping asylum seekers on its side of the border. When Karl replied that “none of that is Mexico paying for the wall,” Mulvaney finally admitted, “You and I both know that it cannot work exactly like that.”

Karl then asked whether the White House would accept a compromise proposed in Sunday’s Washington Post by former House Speaker Newt Gingrich and former Post publisher Donald Graham: Trump gets money for a border wall while the “Dreamers” get a path to citizenship. Mulvaney demurred, then said, “The president has made it very clear, however, that he is willing to discuss a larger immigration solution.” He added, “We are more than interested in talking about larger agreements. No one’s actually shown any interest in doing that.”

He left out that there have long been the votes in the House and the Senate for a big immigration compromise, if the president were willing to sign it. The blame lies with the White House, not Congress.

Finally, Karl inquired whether Trump would “bear some responsibility” for what is on track to be the worst December for stocks since the Great Depression. Mulvaney responded decisively, “Oh, no. The fundamentals are still strong.”

Strong? As The Post’s Heather Long reported last week, “a growing number of business leaders and economic forecasters believe that a recession is coming in 2020.” Federal Reserve Chairman Jerome Powell admitted that the economy was “softening.” The Fed downplayed how much it will increase interest rates next year, a sign of diminishing confidence. And on Sunday afternoon, news broke that Treasury Secretary Steven Mnuchin had called the heads of major banks amid concerns about market stability. Mulvaney’s words eerily echoed those of former Sen. John McCain, R-Ariz., who insisted repeatedly until the closing weeks of his 2008 campaign that the “fundamentals of our economy are strong.”

In each of these instances, the incoming White House chief of staff tried to mislead Karl and viewers rather than admit uncomfortable realities. No wonder he and Trump have gotten along.

That said, how long Mulvaney’s tenure will last is anyone’s guess. Axios reports that Trump is already “furious” with Mulvaney over that 2016 video, and CNN’s resurfacing of a 2015 video in which Mulvaney called the border wall “absurd and almost childish” is unlikely to go over well. The Democratic House is about to make life far worse for the White House. Don’t be surprised, then, if Mulvaney finds a quick way to hand off this poisoned chalice.

Again, no one expected Trump to appoint a tremendous chief of staff. Even the most sterling staffers in his White House and Cabinet have faltered. But with stocks plunging, a Democratic House incoming and signs increasing that special counsel Robert Mueller is wrapping up his investigation, now is an especially crucial moment for Trump to have a chief of staff who could restore competence even briefly. Mulvaney, as his dissembling Sunday showed again, is not that person.

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