GOP Sen. Sasse: 'A lot that's troubling' in events around Comey's firing

Sasse was a prominent critic of Trump during the campaign.

"This is a decorated Marine through to U.S. attorney to head of the criminal division to bipartisan applauded head of the FBI for 12 years," Sasse said of Mueller. "Lots of good stuff for the American people to put hope in about the fact that Bob Mueller is going to conduct that investigation."

With Mueller’s appointment, he said, “We all need to be looking forward to the task of trying to rebuild trust in a lot of these institutions” of government, including the FBI.

Sasse was a well-known member of the ‘Never Trump’ movement during the 2016 campaign who questioned then-candidate Trump's understanding of the Constitution and the U.S. government's system of checks and balances.

Asked by Stephanopoulos if the concerns he expressed during the campaign are proving true, Sasse said that the erosion of a shared understanding of U.S. civic values was happening before Trump was elected.

"We've had an erosion of an understanding of basic American civics for decades,” he said. “But, yes, I am concerned that at this particular moment, there's not enough long-term thinking about how we restore an understanding of the American structure of government."

"I wish that everybody in government, including in particular the president, would spend a lot more time and energy saying [in] five and 10 years from now, am I going to have contributed to a world where American kids understand why the First Amendment is so glorious?” Sasse said.