Why is this all moving so quickly?

My colleague Mike Schmidt, who helped break the story last night about American envoys drafting a statement for Ukraine’s president, called me this morning as he was eating breakfast to help me answer that question.

Mike, you covered Robert Mueller for two years. That investigation — the evidence-gathering and writing of the report — felt relentlessly plodding. This impeachment inquiry feels like it’s moving at Mach speed. Why?

Mueller was premised on the idea that his investigators had to do their work in secret and then would release what they found. It was this self-contained thing inside the Justice Department, operating under the rules of a federal investigation that are designed to shield work from the public. Then you basically got a big dump of Thanksgiving dinner — the report — and you were supposed to sit there and try to wade through it.

What makes this impeachment investigation so different from one run by professional prosecutors?

The witnesses are scurrying to get their side out publicly to make sure it doesn’t look like they were enabling the president. It propels the story forward at an incredible speed. These inspectors general, like Mr. Atkinson today, are not bound by the same rules of a federal investigation. They’re sort of like free agents and can largely make reports to Congress without going through the Justice Department.

So should Democrats in Congress be grateful that they’re the investigators this time around?

A lot of times, Congress is impeded by a federal investigation and can’t get to a lot of the evidence or witnesses, because the F.B.I. says, “We’re conducting an ongoing investigation.” That’s a huge chill. While Democrats are upset there isn’t an F.B.I. investigation, it has still freed up witnesses to cooperate with them. They benefit from being able to do it themselves.