Keep in mind, this is the same guy who tweeted mere week ago that Robert Mueller is a consummate professional, and that the media ought to just calm down now and let him do his work. What happened?
Apparently what happened is that Mueller has started building his team of investigators, and Newt has noticed that they're not only all Democrats but they all have a history of giving money to Democrat candidates. One worked for the Clinton Foundation. Newt's conclusion: They're "bad people" (!) who will be out to get Trump.
George Stephonoupolous takes exactly the stance you'd expect, but Newt doesn't back down: