‘What does Trump fear about Flynn?‘: Morning Joe panel asks why Trump is risking presidency for Flynn
Lieutenant General Michael Flynn (ret.), National Security Advisor Designate speaks during a conference on the transition of the US Presidency from Barack Obama to Donald Trump at the US Institute Of Peace in Washington DC, January 10, 2017 (AFP Photo/CHRIS KLEPONIS)

A "Morning Joe" panel discussed the continuing revelations of ties between the Trump campaign and Russia -- and pointed to disgraced national security adviser Mike Flynn as the nexus of the ongoing scandal.

"The ghost of Michael Flynn hangs over this White House," said MSNBC's Willie Geist, filling in for hosts Joe Scarborough and Mika Brzezinski.

Democrats on the Senate Intelligence Committee, which is investigating Trump's ties to Russia, have suggested that Flynn may be cooperating with the FBI, which has been conducting its own investigation for nearly a year.

"One of the great mysteries that continues to be at the center of this entire story, upon which the future and the fate of the Trump presidency may hang, is, what is it that Donald Trump fears about Michael Flynn?" said MSNBC's John Heilemann.

"He has exposed himself to enormous political and legal risk, in trying to, first, put Flynn in that job, keep him in that job and then protect him, make the investigation go away, if you believe (former FBI director) Jim Comey," he continued. "What is it that Michael Flynn knows about Donald Trump, if anything, that has Donald Trump acting so afraid of what could befall him, if that information became public? I don't know the answer to that question, but I think that is at the core of this entire story."

Panelist Katty Kay, of BBC News, suggested that Trump might simply be "fantastically loyal" to Flynn for his support during the presidential campaign -- but Heilemann wasn't buying that.

"I'd like to point to the historical evidence of Donald Trump behaving that way toward almost anyone in his life," Heilemann said.