And in many cases, they seem to have known about contacts with Russia that the campaign and its principals, including President Donald Trump, would later deny.
Below are seven big questions we have in light of the plea deal.
1. Who is the "campaign supervisor" with whom Papadopoulos emailed in detail about setting up a Trump-Putin meeting?
After a March 24, 2016, meeting with an unnamed London professor and an unnamed Russian national whom Papadopoulos at one point believed to be Vladimir Putin's niece, Papadopoulos emailed a "Campaign Supervisor and several members of the Campaign's foreign policy team," according to the document. He told them the meeting was to set up another meeting between the campaign and "Russian leadership to discuss US-Russia ties under President Trump".
The "Campaign Supervisor" at this point replied: "Great work."
Later, about June 1, Papadopoulos emailed the same "supervisor" to say that a "Russian MFA" wanted to set up a meeting between Trump and Putin. The supervisor urged Papadopoulos to make the trip with another foreign policy adviser instead.
The campaign and the White House have repeatedly denied contacts with Russia during the 2016 race. The denials even came from Trump himself and Vice-President Mike Pence. But this particular set of emails (and more to come below) suggest several members of the campaign were aware of contacts discussing a desire on behalf of the Russian Government to broker a meeting.
2. Who is the Trump campaign official who urged that the meeting not include Trump "so as not to send any signal?" And what does that even mean?
In a tantalising footnote, someone described as a "high-ranking official" on the Trump campaign forwarded a Papadopoulos email to another official in late May and said, "We need someone to communicate that DT is not doing these trips. It should be someone low level in the campaign so as not to send any signal."
So yet again, we have a top official in the campaign who was aware of Papadopoulos's contacts with Russia - Papadopoulos titled the email "Request from Russia" - and thought it through enough to offer a different course of action. Along with the "supervisor" and members of the foreign policy team above, that's another apparently high-ranking Trump campaign official who knew about this. How could the campaign and White House go on to deny such contacts?
Also juicy here: What does "so as not to send any signal" mean? Some see that as a potential tell when it comes to a larger effort to coordinate with the Russians, which is the big unanswered question in this whole investigation. But it could also simply be that they didn't want to telegraph a close alliance with Russia, which could have been politically problematic.
3. Was Trump present when Papadopoulos said that he could set up a Trump-Putin meeting?
The indictment says Papadopoulos attended a "national security meeting" on about March 31 with "Trump and other foreign policy advisers for the Campaign." It says Papadopoulos told "the group" that he had connections and could arrange a Trump-Putin meeting.
The text doesn't say whether Trump was present for this claim. But if he was, it would render Trump's own denials of his campaign's contact with Russia pretty dishonest.
4. Who is the "senior policy adviser" Papadopoulos emailed saying Russia had an "open invitation" for a Trump-Putin meeting?
This is yet another high-level aide who would have known there was contact with Russia. Papadopoulos told this "adviser" on April 25 that "these governments tend to speak a bit more openly in 'neutral' cities" - playing up his own stationing in London.
5. Who is the other "high-ranking official" whom Papadopoulos told that the Russian Government had "relayed to me that they are interested in hosting Mr Trump?"
This is a different "high-ranking official" than the one mentioned above. But it's another person who apparently knew, based on multiple emails, about what the campaign and White House would later deny.
6. Who is "Putin's niece?"
It may be neither here nor there in this whole sequence, but Papadopoulos seems to have believed at one point that the unnamed London professor introduced him to Putin's niece, identifying her as such in an email to the campaign. He later says it wasn't actually Putin's niece.
But who was it? And did Papadopoulos not seek to verify this information? Or was he trying to inflate his connections in the email? It's all very strange.
And for that matter, who is the unnamed London professor?
7. What is he doing to cooperate?
At the very end, the indictment says Papadopoulos was arrested at Dulles International Airport in suburban Washington on July 27 of this year. It says he has talked with the Government "on numerous occasions to provide information and answer questions."
It is suspected that the special counsel is trying to flip Paul Manafort and get him to cooperate via his own indictment. Papadopoulos was far less central to the campaign, but here we actually have someone who is cooperating.
What did he agree to share in his plea deal? And what does he even have to share? This may be the biggest question of all.
