In a sprawling investigation spanning nearly two years, Special Counsel Robert Mueller examined two burning questions: Did President Donald Trump or any of his associates conspire with Russia’s efforts to interfere in the 2016 presidential election and did Trump commit obstruction of justice during the investigation?

A four-page summary of Mueller's highly anticipated report -- sent in a letter by Attorney General William Barr to congressional leaders and the media -- provides at least some of the answers.

Collusion Not Established

The summary said the Mueller investigation did not find that Trump or any American associated with his campaign conspired with Russia to influence the 2016 election, which would be a federal crime.

“[T]he investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities,” Barr quoted Mueller as writing in his report.

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The summary said one of the two main ways Russia tried to influence the election was through the Internet Research Agency (IRA), a St. Petersburg-based "troll factory" allegedly controlled by Kremlin-connected businessman Yevgeny Prigozhin.

Barr said the IRA attempted to “conduct disinformation and social-media operations in the United States designed to sow social discord, eventually with the aim of interfering with the election.”

But Mueller did not find that any “U.S. person or Trump campaign official or associate conspired or knowingly coordinated with the IRA in its efforts,” according to Barr’s summary.

The summary said the other chief way the Russian government tried to influence the election was by hacking material from Democratic organizations that WikiLeaks released at critical junctures in the weeks before the election. They included thousands of stolen e-mails from the private account of Democratic candidate Hillary Clinton's campaign chairman, John Podesta, in the closing weeks of the campaign.

Although Mueller brought criminal charges against Russian military officers, the special counsel “did not find that the Trump campaign, or anyone associated with it, conspired or coordinated with the Russian government in these efforts, despite multiple offers from Russian-affiliated individuals to assist the Trump campaign,” Barr said in the summary.

William Barr (file photo)

Barr said that Mueller "thoroughly" investigated the question of whether the Trump campaign coordinated with Russia's election interference, issuing more than 2,800 subpoenas, obtaining nearly 500 search warrants, and interviewing 500 witnesses.

Did He Or Didn't He?

On the issue of whether Trump obstructed justice, the outcome of Mueller’s investigation was less clear-cut.

According to Barr's summary, Mueller's report states that while it "does not conclude that the President committed a crime, it also does not exonerate him."

Barr said that Mueller -- for reasons the attorney general did not explain in detail -- decided not to "draw a conclusion" as to whether Trump, in his view, committed the crime of obstruction of justice.

Instead, Barr said, Mueller's report examines Trump's actions and "sets out evidence on both sides of the question."

Mueller’s report “leaves unresolved what the Special Counsel views as ‘difficult issues’ of law and fact concerning whether the President’s actions and intent could be viewed as obstruction,” Barr added.

But Barr and Deputy Attorney General Rod Rosenstein concluded that the evidence was "not sufficient to establish that the president committed an obstruction of justice offense," the summary said.

Barr, nominated to his job by Trump last year, said their decision was based on the evidence uncovered by Mueller and was made "without regard to" the constitutional question of whether a sitting president can be indicted.

In a possible nod to Trump's public attacks on investigators and witnesses, Barr said Mueller had cataloged the president's actions, “most of which have been the subject of public report.”

Rod Rosenstein (file photo)

Zeke Miller, a White House reporter for the AP, said in a tweet that the wording of the letter suggested that “at least one action of the president that was investigated as potential obstruction of justice...has yet to be revealed in public reporting.”

Many of Trump’s opponents accused him of obstructing the Russia probe when he fired FBI Director James Comey in May 2017. Mueller was subsequently appointed to conduct the investigation into Russia's role in the campaign.

Trump's shifting explanations for why he fired Comey had fueled suspicions that it was aimed at halting the FBI investigation, which began in July 2016.

Some legal experts have said that in itself may have constituted a federal crime -- obstruction of justice -- an allegation that figured prominently in the impeachment-related proceedings of Presidents Richard Nixon in 1974 and Bill Clinton in 1998.