Morning Joe regulars discussed the known fact that Mike Flynn is highly motivated to save his son from going to prison.

"And because of that, is trying to figure out how he can help Mueller and prove to Mueller that he has something to give up. It was a pretty significant development, we thought," Joe Scarborough said

"Equaling troubling to the Trump team, somebody was actually in an information-sharing arrangement to get all the information from the Trump team as they were preparing to mount a defense against Mueller, who has now broken away," he said. "Along with breaking away, they also have all that information that they've been gathering. So that makes a bad situation even worse for the Trump team. Doesn't it?"

"It does. If you remember earlier this year, Flynn's lawyer said when we were reporting that Flynn was immunity from investigators that Michael Flynn has a story to tell," reporter Carol Lee said.

"If you're the White House and you're the president's legal team and you don't have eyes into exactly what story he's telling, that could be concerning. They're trying to distance themselves from Flynn," Lee said.

"You have a White House official telling Kristen Welker that Flynn is taking steps that are in his best interest, to deal with, quote, 'things that are unique to him.' Flynn was in the White House. We know that Robert Mueller is looking at some of his activity while serving as national security adviser. This is a potentially very significant development and gets this much closer to the White House than we've seen previously."

Scarborough told John Heilmann he'd always been told by the Trump campaign that General Flynn was "always on the plane with Donald because he kept Donald calm."

"He'd sit with him all the time, kept him in check and said you know he's a very moderating influence on Donald. We want him sitting next to Donald at all times, especially when they're flying long distances. These two were extraordinarily close," Scarborough said.

"You think about the two -- in building this case, whatever the case is that mueller ends up with the two people at the most focus are Paul Manafort and Michael Flynn," Heilemann said.

"They are orders of magnitude different, in other words, to their proximity to Trump and amount of time they spent with Trump, both as Carol points out --because Flynn was not just a player in the campaign but for a brief time was at the pinnacle of power at the White House before he was fired.

"But also Manafort was around for six months or so, and then there was some communication that continued, but he was not ever on the plane with Donald Trump every single day. It is the case that Flynn flew around the country with Trump constantly, was the person who was at the top of the foreign policy apparatus, the person who had conversations with Trump constantly about the pertinent question at issue, Russia.

"This is a question Flynn discussed with him in normal settings, informal settings, on the fly, during the campaign, in the formidable stages and in the White House. I'm not discounting how important Manafort is, but Flynn in terms of what he could give to Robert Mueller and his team is infinitely -- infinitely more consequential."