ANALYSIS: While the biggest news of the day is the indictments Robert Mueller has handed down against former President Donald Trump aides Paul Manafort and Rick Gates, he also released a plea bargain with a heretofore minor figure in the Russia scandal by the name of George Papadopoulos. And that could actually be the day's biggest news.

That's because while Manafort and Gates sure look like they're going to jail, as of yet they aren't cooperating with Mueller's investigation. Papadopoulos is, which means that he likely has information that will lead Mueller closer to the heart of the case.

Papadopoulos was a junior foreign policy adviser to the Trump campaign. In August we learned that he had tried to set up meetings between Trump officials – and even Trump himself – with representatives of the Russian government. At the time, his suggestion was characterised as having been rejected by other Trump officials as inappropriate while Trump was still a candidate and not yet president.

GEORGE PAPADOPOULOS/TWITTER George Papadopoulos, a former foreign policy adviser to US president Donald Trump, has pleaded guilty to lying to the FBI.

But now that we've seen the details of Papadopoulos' plea, it sure looks like that wasn't the whole story.

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Papadopoulos has agreed to plead guilty to lying to the FBI about his contacts with Russians. Specifically, he falsely claimed that they had occurred before he joined the campaign in March 2016. He had communication with a professor who had contacts in the Russian government; this professor told him that the Russians had "dirt" on Hillary Clinton in the form of "thousands of emails". The professor introduced him to a female Russian national who was supposedly Vladimir Putin's niece (it turned out she wasn't), and to someone who supposedly had connections in the Russian Ministry of Foreign Affairs (MFA). Based on those conversations, Papadopoulos pressed the campaign to set up meetings with the Russians, a suggestion that never came to fruition.

JONATHAN ERNST/REUTERS Federal agents transport former Trump campaign manager Paul Manafort (back seat) to the federal courthouse in Washington DC.

So what does this have to do with the larger case? I spoke this morning with Barbara McQuade, a professor at the University of Michigan law school who is a former US Attorney and has worked extensively in criminal and national security cases. I asked: If Papadopoulos was just some low-level nobody tossing around ideas that were rejected by the campaign's higher-ups, why would Mueller offer him a plea deal that is contingent on his cooperation? Doesn't that suggest that he has information that can be used to build a case against someone more important than him?

"I think it's a fair conclusion to think that he has information that is valuable in the prosecution of others," McQuade says. "You would only offer that cooperation if you've sat down with him and learned that he has information that is of value."

And that appears to be what is happening: in return for what will likely be a reduced sentence, Papadopoulos has agreed to sing. As the letter laying out the terms of the plea agreement says, "The Government agrees to bring to the Court's attention at sentencing the defendant's efforts to cooperate with the Government, on the condition that your client continues to respond and provide information regarding any and all matters as to which the Government deems relevant."

Who does Papadopoulos have information on? We don't know. The plea document mentions his discussions (his efforts to set up a meeting with the Russians) with people who are referred to as "Senior Policy Adviser," "Campaign Supervisor," and "High-Ranking Campaign Official," but we don't know who that is. Then there's this:

"On or about May 4, 2016, the Russian MFA Connection sent an email (the 'May 4 MFA Email') to defendant PAPADOPOULOS and the Professor that stated: 'I have just talked to my colleagues from the MFA. The[y] are open for cooperation. One of the options is to make a meeting for you at the North America Desk, if you are in Moscow.' Defendant PAPADOPOULOS responded that he was '[g]lad the MFA is interested.' Defendant PAPADOPOULOS forwarded the May 4 MFA Email to the High-Ranking Campaign Official, adding: 'What do you think? Is this something we want to move forward with?' The next day, on or about May 5, 2016, defendant PAPADOPOULOS had a phone call with the Campaign Supervisor, and then forwarded the May 4 MFA Email to him, adding to the top of the email: 'Russia updates.' "

This exchange happened not long before Paul Manafort, Donald Trump Jr, and Jared Kushner had their infamous meeting with representatives of the Russian government who purportedly had damaging information on Clinton to offer. Given that context, it seems rather unlikely that Papadopoulos would not have mentioned the possibility that the Russians had of "dirt" on Clinton contained in "thousands of emails." But we don't yet know for sure.

YURI GRIPAS/REUTERS Special prosecutor Robert Mueller is trying to get to the heart of the Trump campaign's relationship with Russia.

What we do know is that the prosecutors believe that Papadopoulos' information will be valuable to them in building a case against others. Paul Manafort, on the other hand, is not cooperating – at least not yet. "The fact that he was indicted suggests to me that pre-indictment he said 'No, I don't want to cooperate.' I'm sure they presented him with the opportunity," says McQuade. It's a common tactic to hand down one set of indictments and then offer a defendant the chance to start cooperating, since if he doesn't they'll keep investigating, and who knows what else they'll find. "I think that's quite possible, that there are additional potential charges against Manafort, and he could still cooperate," McQuade said.

If Manafort is going to flip, there are only so many people he could flip on, who are actually closer to the centre of whatever happened than he was. That could include Jared Kushner, perhaps Donald Trump Jr, and of course President Trump himself.

But right now, Papadopoulos is the one who is providing Mueller an entry into the heart of the Trump campaign and its relationship to Russia. Which is why McQuade says, "That one, because of its relevance to that larger question, strikes me as maybe the more important development today." And this is just getting started.