Michael Flynn, who served as President Donald Trump’s national security adviser for just 24 days before being cut loose, may be the key figure to unraveling the entire Russia scandal. If that’s true, the president just got some very, very bad news in the form of a New York Times report:

Lawyers for Flynn notified the president’s legal team in recent days that they could no longer discuss the special counsel’s investigation, according to four people involved in the case - an indication that Flynn is cooperating with prosecutors or negotiating a deal.

Flynn’s lawyers had been sharing information with Trump’s lawyers about the investigation by the special counsel, Robert Mueller, who is examining whether anyone around Trump was involved in Russian efforts to undermine Hillary Clinton’s presidential campaign.

That agreement has been terminated, the four people said. Defense lawyers frequently share information during investigations, but they must stop when doing so would pose a conflict of interest. It is unethical for lawyers to work together when one client is cooperating with prosecutors and another is still under investigation.

We should be clear that this news is not definitive proof that Flynn is cooperating with Mueller. It may mean only that he is in the process of negotiating a deal to avoid prosecution, and that deal might or might not involve giving information on other figures in the investigation. But if Flynn is indeed cooperating, Trump is in big trouble.

That’s because if Flynn is cooperating, it can only be because he has information to offer Mueller on someone more important than himself. That’s how it works. And who is more important than Flynn? Only a very small number of people. Among those implicated in this whole affair, that group may consist of Jared Kushner and Trump, and that’s about it.

Which means we may be getting closer to answering a question I’ve been asking for a long time: Why was President Trump so intensely focused on protecting Michael Flynn?

You’ll recall that Flynn was supposedly fired because he lied to Vice President Mike Pence about his contacts with Russian officials during the campaign and the transition, claiming he had only exchanged pleasantries with them when in fact they had discussed substantive policy matters, something Pence then repeated to the media. This was always an odd explanation for the firing. Even more odd was the fact that immediately, Trump began telling anyone who would listen what a great guy Michael Flynn is and how unfair the whole mess was to him.

Given that Trump is not known for being loyal to those who work for him, that was rather curious. Donald Trump looks out for Donald Trump, and if you become a liability to him, he’ll very quickly start acting as though he barely knew you. Now consider what Trump proceeded to do with regard to Flynn:

The day after Flynn resigned, Trump asked then-FBI Director James Comey to stop investigating the former national security adviser. “I hope you can let this go,” Comey reported Trump saying in a memo he wrote immediately after their meeting.

Trump asked Director of National Intelligence Daniel Coats to intervene with Comey to get him to back off his investigation of Flynn.

Unlike with previous aides who have displeased him, after he fired Flynn, Trump made a very public show of praising him to the media.

Months after Flynn was fired and as the investigation was accelerating, Trump kept in contact with Flynn. “I just got a message from the president to stay strong,” Flynn told friends at a dinner in April.

In May, Trump scolded his staff for criticizing Flynn to the media and had his spokesmen issue statements lavishly praising Flynn.

It’s almost as though Trump wanted to make sure Flynn didn’t turn on him.

But if Flynn is turning on Trump, it’s because he is in a whole lot of legal trouble, probably more than anyone involved in this scandal with the exception of former Trump campaign manager Paul Manafort. Let’s remember that shortly after the Trump administration began, acting attorney general Sally Yates went to the White House and informed officials that Flynn had lied to the FBI about his contacts with Russian officials (which they knew because they were monitoring the Russian ambassador’s communications) and that because of those lies, he was susceptible to blackmail. For some reason, Flynn spent 18 more days in the White House before being fired.

By taking a large fee from Russia for giving a speech in late 2015, Flynn appears to have violated a law that requires retired generals getting such payments to receive prior approval. He also was hiding the fact that he was paid more than half a million dollars by allies of the Turkish government to promote Turkey’s interests while advising the Trump campaign (he later registered retroactively as an agent of a foreign government; failing to register is a felony). He failed to include payments from Russia on his financial disclosure forms and may have lied about it to investigators. During the transition, he managed to delay a military operation against the Islamic State that Turkey objected to while he was secretly receiving those Turkish payments, a story that has gotten strangely little attention. He was even reportedly involved in planning for a bizarre plot to kidnap the exiled Turkish cleric Fethullah Gulen in Pennsylvania and return him to Turkey, for which Flynn and his son were allegedly to be paid $15 million.

In short, Flynn appears to have violated multiple laws in multiple ways and could be looking at the possibility of serious time behind bars. He may have information Mueller could use in a case against Kushner, Trump or others, relating to multiple strands of the investigation. He may know things about the campaign’s relationship with the Russian government or about an obstruction of justice case related to Comey’s firing. Don’t forget that Trump admitted on national television that he fired Comey to shut down the Russia investigation, then shortly thereafter told the Russian foreign minister and ambassador that with his firing of Comey, “I faced great pressure because of Russia. That’s taken off.”

Here’s what we should watch for now: If the White House suddenly changes how it talks about Flynn, disparaging him instead of saying what an admirable fellow he is, that’ll be a good indication of a change in Trump’s feelings. And it looks as though he has a lot to be nervous about.