The memo showing President Donald Trump asked then-FBI director James Comey to stop an investigation represents a "serious situation." But it's far from the Watergate scandal that took down former President Richard Nixon, John Kasich said Tuesday.

"We're a long way away from anything like that," the Ohio governor said, comparing turmoil in the Trump White House to the Watergate scandal that led to the impeachment and resignation of former President Richard Nixon. "I don't think that we know exactly what happened," he said, calling for investigations into the Comey memo and whether Trump associates were involved in Russian attempts to influence the 2016 election.

Kasich joined Democratic presidential runner-up Bernie Sanders on CNN Tuesday night. The two originally had agreed to a debate. CNN changed the format after the New York Times first reported Comey had written a memo about Trump's asking him to stop an investigation into former national security adviser Michael Flynn.

"We have to get to the bottom of this," Kasich told CNN. "This is not a time for Republicans to hide, and I also don't think it's a time for Democrats to exploit."

The "things that have swirled around this White House" – from allegations that Trump shared classified information with the Russian foreign minister to Trump's firing of Comey amid an FBI investigation into the president's associates – are what Kasich feared when he refused to endorse Trump, the Ohio governor said.

Still, when pressed by Sanders, Kasich stopped short of calling Trump a "liar."

"Sometimes he says things I don't agree with, and I think they don't resemble the facts," Kasich said.