A former National Security Council aide feared Gordon Sondland, the ambassador to the E.U. and one of Mr. Trump’s go-to diplomats for Ukraine, was a national security threat because of his extreme inexperience — likening him to someone driving in an unfamiliar place with no guardrails and no GPS. Tomorrow, Mr. Sondland will finally be interviewed by impeachment investigators. I asked my colleague Michael Crowley, who covers White House foreign policy, about him.

Michael, what makes Mr. Sondland, a wealthy hotel owner and longtime political donor, such an odd fit as a diplomat?

Many people thought Mr. Sondland was unqualified even for the job he was supposed to be doing as ambassador to the E.U. His predecessor in that job had decades of diplomatic experience and had several advanced degrees. The E.U. has 28 member states and has just a very complicated, important relationship with the U.S. that involves economics, diplomacy and security issues.

So then how did he end up as Mr. Trump’s quasi-fixer in Ukraine?

You often see donors who at least appear to have bought their way into ambassadorships who then kind of keep their heads down, enjoy the job, revel in the title and the glamour. Mr. Sondland comes in like a mini Trump. He’s disrupting. He’s offending. Rather than many diplomats kind of buttering up their host countries, he comes in saying, “The E.U. is out of touch. It’s ripping the U.S. off. The party’s over.” He didn’t show much interest in diplomatic protocols. I spoke to one person for the story who said he is one of the Trumpiest of Trump’s ambassadors.