Impeachment investigators have been gathering evidence for weeks to prove what Mr. Mulvaney freely admitted to reporters in the White House Briefing Room. I talked to my colleague Maggie Haberman about why he said something so stunning.

Maggie, whoa. That happened in front of reporters at the White House.

The briefing was jaw-dropping by any metric. He admitted to a quid pro quo. But it showed once again something you and I talked about two weeks ago: Mr. Trump tries to shift the window on conduct by revealing stuff publicly to take the sting out of its discovery. Mr. Mulvaney insisted the terminology doesn’t matter, but he bluntly acknowledged that aid was withheld from Ukraine to get a desired outcome on an investigation. That is at the heart of what Democrats have been trying to ascertain.

Was it actually the plan for him to do this?

I do think it was, yes — at least in part. Remember, this happened as Mr. Sondland was on the Hill giving a closed-door deposition . So I think Mr. Mulvaney was trying to rob House Democrats of a headline and frame the events on his own, to take the air out of the sails by saying it out loud. But it’s not clear that he was actually supposed to say there was a quid pro quo. It’s breathtaking that he’s the first person they’ve sent out to expressly discuss these issues and that he said so much.

How might this affect the impeachment investigation?

He came out and admitted to a lot of what House Democrats were hoping to get from him in a deposition! I can’t imagine the White House counsel and others were thrilled. Mr. Mulvaney and the counsel’s office have been at odds lately.