A big question clouding American politics for more than two years was whether anybody from President Donald Trump’s winning campaign assisted in Russia’s interference in the 2016 U.S. presidential election. Special Counsel Robert Mueller’s criminal investigation, in producing indictments against Russian nationals and former Trump advisers, dropped hints that some people in the Trump campaign had at least wanted to play ball with Russia. In the end, though, Mueller’s team concluded there was no conspiracy or coordination, just as Trump has long said.

1. What did Mueller conclude?

Mueller’s final report says the investigation “did not establish that members of the Trump campaign conspired or coordinated with the Russian government in its election interference activities,” according to the four-page letter Attorney General William Barr delivered to Congress. This was despite “multiple offers from Russian-affiliated individuals to assist the Trump campaign,” Barr wrote.

2. What clues pointed to the campaign’s involvement?

An intriguing one involved Roger Stone, a political operative who advised Trump. He hinted during the 2016 campaign that he knew in advance that the anti-secrecy group WikiLeaks would release unflattering information hacked from the campaign of Trump’s Democratic rival, Hillary Clinton. Since that hacking was carried out under the guidance of Russian intelligence, according to U.S. investigators, Stone — who was arrested on Jan. 25 on charges of witness tampering and making false statements — was seen as a possible link between Trump and the Russian election interference. Furthering that idea, Trump’s onetime personal lawyer, Michael Cohen, says he overheard Stone tell Trump that he was communicating with WikiLeaks founder Julian Assange about “a massive dump of emails that would damage Hillary Clinton’s campaign.”

3. What was in those emails?

First, WikiLeaks released almost 20,000 emails from inside the Democratic National Committee that showed how staffers there had favored Clinton during her primary campaign against Senator Bernie Sanders. That prompted the resignation of the DNC’s chairman, Debbie Wasserman Schultz. Later, WikiLeaks released tens of thousands of emails from the Gmail account of John Podesta, Clinton’s campaign chairman; this email dump is the one that Stone seemed to know was coming. The material hacked from Podesta produced unflattering headlines about Clinton saying politicians “need both a public and private position” on tough issues; Clinton allegedly being fed in advance a question that would be posed during a televised debate; and Clinton speaking of her “dream” of “a hemispheric common market, with open trade and open borders.” Looking back on her defeat, Clinton said the “WikiLeaks email dumps” had been “like Chinese water torture.”

4. What other clues were there?

Paul Manafort, chairman of Trump’s campaign for two months, may have shared polling data with an associate tied to Russian intelligence. Former Trump foreign policy adviser George Papadopoulos pursued Russia’s help in the campaign and interacted with a suspected Russian agent who promised compromising information about Clinton. And as Trump was sewing up the Republican Party’s nomination in June 2016, a Russian lawyer offering information on Clinton was granted a meeting at Trump Tower in New York with Trump’s eldest son, Donald Jr.; Trump’s son-in-law, Jared Kushner; and Manafort.

5. What did Mueller conclude about all this?

That’s not known, since Mueller’s report to Barr is still secret. Democratic lawmakers have demanded the full report as well as the underlying evidence so they can pursue their own investigations. Mueller’s team of investigators and prosecutors charged six former Trump advisers, 26 Russian nationals and three Russian companies. Five of the six former Trump advisers have pleaded guilty, though none to charges of helping Russia interfere with the election. (Stone, the sixth, has vowed to fight his charges in court.) A former Federal Bureau of Investigation director, Mueller was called back into service as special counsel to oversee the probe. Eight days before his appointment, Trump had fired the head of the FBI, James Comey, who’d been a key player in the investigation.

6. How did this all begin?

In April 2016, Democratic Party leaders called in a cybersecurity firm to look at suspicious software on their computers. The firm said it found digital footprints of hackers tied to the Russian government. The Democratic National Committee went public with the news and the suspicion of Russian involvement in June of that year, just after Clinton clinched the party’s nomination for president, and just after Assange said his group had “upcoming leaks in relation to Hillary Clinton.”

7. And WikiLeaks got those emails from Russia?

That’s the allegation. U.S. intelligence agencies concluded that Russian President Vladimir Putin ordered a campaign to undermine “public faith in the U.S. democratic process” and Clinton’s candidacy, and that along the way, Putin and his government “developed a clear preference” for Trump. Russia’s efforts included hacking and leaking the emails that undermined Clinton’s campaign, plus using phony accounts and advertising on Facebook and Twitter to sway American public opinion. U.S. intelligence says Russia’s General Staff Main Intelligence Directorate, or GRU, gave the emails to WikiLeaks through an intermediary. Some of the emails also were released through the “persona” of a purported Romanian hacker, Guccifer 2.0, and a website, DCLeaks.com, both of which promoted the hacked information to certain journalists.

8. How does Assange respond?

From the Ecuadorian Embassy in London, where he lives under political asylum, Assange has denied that the Russian government was his source of the hacked emails. But an indictment released by Mueller in July 2018, charging 12 Russian military intelligence officers allegedly assigned to disrupt the U.S. election, said that WikiLeaks asked Guccifer for the hacked emails in order to help promote them in advance of the Democratic National Convention, and that Guccifer responded with instructions on how to access them.

9. What does Putin say?

The Russian leader confirmed he did in fact want Trump to win the election but said that was only because Trump was interested in improving U.S.-Russian relations. As for allegations of meddling in the U.S. election, Putin called them “utterly ridiculous.”

10. What does Trump say?

He has always insisted that no evidence would emerge of “collusion,” which in legal terms would translate to conspiracy. Trump dismisses as a “total hoax” the suggestion that his campaign welcomed Russian interference.