Lisa Desjardins:

Two reasons.

It helps them in court to say, we need to exercise a very prominent constitutional authority, because we believe the president may have done something impeachable. That has in the past made a difference in court hearings — in our rulings.

The other, Judy, is political. We have known Democrats for weeks have been in favor or not in favor of an impeachment inquiry. The semantics have been a problem for Democrats. Now they're trying to wash that all away by saying, listen, we have been investigating, and now we are investigating and we are formally saying, this is an impeachment investigation.

They're not going to take a separate vote on whether to open an investigation. They're simply doing it.