Last September, when Donald Trump named his fourth White House national security adviser in three years, it seemed the president may have tapped Robert O’Brien, a State Department official who has specialized in hostage issues, because O’Brien had said nice things about him.

Five months later, it appears O’Brien is still finding unfortunate ways to stay in his boss’ good graces.

White House national security adviser Robert C. O’Brien asserted Wednesday that President Trump had not sought Ukrainian help investigating former vice president Joe Biden and his son, Hunter, despite evidence to the contrary. […] “Look, I’m not aware of any request the president made to investigate the Bidens per se. I think what the president wanted done was he wanted the Ukrainians to investigate corruption in the Ukraine and he made that very clear,” O’Brien said before an audience of ambassadors and reporters at the Meridian International Center.

This comes roughly a week after Deputy White House Counsel Patrick Philbin argued during the Senate impeachment trial that Trump didn’t “necessarily” ask foreign countries to go after the Bidens.

I think there are two relevant angles to keep in mind. The first is that the argument is plainly bonkers.

As we discussed after Philbin’s argument, the White House released an official call summary of Trump’s July 25 conversation with Ukrainian President Volodymyr Zelensky, in which the American president pressed his counterpart in Kyiv to “look into” the former Democratic vice president. “[T]here’s a lot of talk about Biden’s son, that Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the attorney general would be great,” the Republican said in the phone meeting.

Trump continued, “Biden went around bragging that he stopped the prosecution so if you can look into it … It sounds horrible to me.”

I suppose one might quibble with the precise meaning to “look into,” but it was the next day that Trump reportedly asked Ambassador Gordon Sondland, “So, he’s gonna do the investigation?” That seems to remove all doubt as to what the American president meant by “look into.”

But we need not stop there. A week after that call summary was released to the public, Trump stood on the South Lawn of the White House and told reporters on camera, “China should start an investigation into the Bidens.” The Republican added soon after, “I would say that President Zelensky, if it were me, I would recommend that they start an investigation into the Bidens.”

Are we to believe the White House national security adviser didn’t hear about any of this?

Meanwhile, the second angle of note is that O’Brien is serving in an important and influential office, where credibility — with other officials, with the public, with foreign governments — actually matters.

For O’Brien to undermine his trustworthiness the way he did yesterday is a costly mistake for a White House already struggling with a credibility crisis.

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