Attorney General William Barr has provided only a glimpse of Special Counsel Robert Mueller's report on the inquiry into Russia's role in the 2016 U.S. election, with many details expected to emerge when the document is finally released on Thursday.

Barr on March 24 sent a four-page letter to lawmakers detailing Mueller's "principal conclusions" including that the 22-month probe did not establish that President Donald Trump's 2016 campaign team conspired with Russia. Barr said he found insufficient evidence in Mueller's report to conclude that Trump committed obstruction of justice, though the special counsel did not make a formal finding one way or the other on that.

The attorney general has pledged to release the nearly 400-page report by mid-April, but has said portions will be blacked out to protect certain types of sensitive information.

Here are five things to look for when the report is issued.

OBSTRUCTION OF JUSTICE: WHY NO EXONERATION?

Perhaps the biggest political risk for Trump is the special counsel's supporting evidence behind Mueller's assertion that while the report does not conclude the Republican president committed the crime of obstruction of justice it "also does not exonerate him" on that point.

According to Barr's March 24 letter, Mueller has presented evidence on both sides of the question without concluding whether to prosecute. Barr filled that void by asserting there was no prosecutable case. But Barr's statement in the letter that "most" of Trump's actions that had raised questions about obstruction were "the subject of public reporting" suggested that some actions were not publicly known.

Democrats in Congress do not believe Barr, a Trump appointee, should have the final say on the matter. While the prospect that the Democratic-led House of Representatives would begin the impeachment process to try to remove Trump from office appears to have receded, the House Judiciary Committee will be looking for any evidence relevant to ongoing probes into obstruction of justice, corruption and abuse of power by the president or others in the administration.

Barr's comment that most of what Mueller probed on obstruction has been publicly reported indicates that events like Trump's firing of James Comey as FBI director in May 2017 when the agency was heading the Russia inquiry are likely to be the focus of this section of the report.

RUSSIAN 'INFORMATION WARFARE' AND CAMPAIGN CONTACTS

The report will detail indictments by Mueller of two Kremlin-backed operations to influence the 2016 election: one against a St. Petersburg-based troll farm called the Internet Research Agency accused of waging "information warfare" over social media; and the other charging Russian intelligence officers with hacking into Democratic Party servers and pilfering emails leaked to hurt Democratic candidate Hillary Clinton.

With those two indictments already public and bearing no apparent link to the president, the focus may be on what Mueller concluded, if anything, about other incidents that involved contacts between Russians and people in Trump's orbit. That could include the June 2016 meeting at Trump Tower in New York in which a Russian lawyer promised "dirt" on Clinton to senior campaign officials, as well as a secret January 2017 meeting in the Seychelles investigated as a possible attempt to set up a back channel between the incoming Trump administration and the Kremlin while Democrat Barack Obama was still president.

Any analysis of such contacts could shed light on why Mueller, according to Barr's summary, "did not establish that members of the Trump campaign conspired or coordinated with the Russian government in its election interference activities."

MANAFORT, UKRAINE POLICY AND POLLING DATA

In the weeks before Trump's former campaign chairman Paul Manafort was sentenced in March to 7-1/2 years in prison mostly for financial crimes related to millions of dollars he was paid by pro-Russia Ukrainian politicians, Mueller's team provided hints about what their pursuit of him was really about.

Prosecutor Andrew Weissmann told a judge in February that an Aug. 2, 2016 meeting between Manafort and Konstantin Kilimnik, a consultant Mueller has said has ties to Russian intelligence, "went to the heart of" the special counsel's investigation.

The meeting included a discussion about a proposal to resolve the conflict in Ukraine in terms favorable to the Kremlin, an issue that has damaged Russia's relations with the West. Prosecutors also said Manafort shared Trump campaign polling data with Kilimnik, although the significance of that act remains unclear.

One focus will be on what Mueller ultimately concluded about Manafort's interactions with Kilimnik and whether a failed attempt to secure cooperation from Manafort, who was found by a judge to have lied to prosecutors in breach of a plea agreement, significantly impeded the special counsel's work.

NATIONAL SECURITY CONCERNS

While Mueller did not find a criminal conspiracy with Russia, according to Barr, there is a chance the report will detail behavior and financial entanglements that give fodder to critics who have said Trump has shown a pattern of deference to the Kremlin.

One example of such an entanglement was the proposal to build a Trump tower in Moscow, a deal potentially worth hundreds of millions of dollars that never materialized. Michael Cohen, Trump's former personal lawyer, admitted to lying to Congress about the project to provide cover because Trump on the campaign trail had denied any dealings with Russia.

In the absence of criminal charges arising from Mueller's inquiry, House Intelligence Committee Chairman Adam Schiff has shifted his focus to whether Trump is "compromised" by such entanglements, influencing his policy decisions and posing a risk to national security.

Some legal experts have said the counterintelligence probe Mueller inherited from Comey may prove more significant than his criminal inquiry, though it is not clear to what degree counterintelligence findings will be included in the report. Barr also has said he planned to redact material related to intelligence-gathering sources and methods.

MIDDLE EAST INFLUENCE AND OTHER PROBES

Another focus is whether Mueller will disclose anything from his inquiries into Middle Eastern efforts to influence Trump.

One mystery is what, if anything, came of the special counsel's questioning of George Nader, a Lebanese-American businessman and consultant to the crown princes of the United Arab Emirates and Saudi Arabia who started cooperating with Mueller last year.

Nader attended the Seychelles meeting. He also was present at a Trump Tower meeting in August 2016, three months before the election, at which an Israeli social media specialist spoke with the president's son, Donald Trump Jr., about how his firm Psy-Group, which employed several former Israeli intelligence officers, could help the Trump campaign, according to the New York Times. Mueller's interest in Nader suggested the special counsel looked into whether additional countries sought to influence the election and whether they did so in concert with Russia.

A lawyer for Nader did not respond to a request for comment.

Barr has said he will redact from the Mueller report information on "other ongoing matters," including inquiries referred to other offices in the Justice Department. That makes it unclear if any findings related to the Middle East will appear in the report.