The release of that report on Monday signalled the end of Durham’s four-year investigation.

It is an affair that has been politically charged from the beginning, with Trump and his allies claiming the FBI’s investigation, led by former FBI Director Robert Mueller, was biased against the former president. Mueller’s investigation led to charges against 34 people and three businesses, but found that while the Trump campaign welcomed Russian efforts to influence the election, there was not evidence to prove collusion or criminal conspiracy.

In turn, critics have accused Trump’s former Attorney General Bill Barr of having his own partisan motives in launching Durham’s probe in 2019, with some noting an indepedent FBI watchdog had already assessed shortcomings in the department’s investigation and implemented an array of reforms.

Here are the key takeaways from Durham’s report.

What did the report say?

Most significantly, Durham’s report said that the FBI at the very least was too hasty in opening its investigation of Trump, saying the department at the time lacked “actual evidence” – including any proof of contact between Trump campaign staff and Russian intelligence agents – and instead relied on “raw, unanalysed and uncorroborated intelligence”. Acting with such speed, Durham’s report said, was a departure from the norm.

He added investigators repeatedly fell victim to “confirmation bias”, ignoring or rationalising evidence that may have undercut their case. He pointed to at least one FBI agent who had “pronounced hostile feelings towards Trump”. The report suggested that the FBI handled the 2016 Trump probe differently than other politically sensitive investigations, including several involving Trump’s Democratic rival, Hillary Clinton.

The report also noted the FBI’s failure to corroborate a single substantive allegation from a dossier that purported to show raw research related to the Trump campaign’s alleged collusion with Russia, amid other misdeeds. The collection was known as the “Steele dossier” after the author, former British intelligence officer Christopher Steele, whose research had been funded by Democrats.

“An objective and honest assessment of these strands of information should have caused the FBI to question not only the predication for Crossfire Hurricane, but also to reflect on whether the FBI was being manipulated for political or other purposes,” the report said, referring to the official name of the FBI’s investigation. “Unfortunately, it did not”.

Also significant was what the report did not include: any new charges related to the FBI’s investigation.

What was new?

A 2019 US Department of Justice inspector general report had already identified many problems with the FBI probe, saying it was both dysfunctional and rushed, but denying that there was evidence of political bias or that the department did not have reason to open the probe when it did.

Beyond that, many of the shortcomings identified by Durham were the same as those flagged in the 2019 report.

The earlier watchdog report had also taken issue with investigators’ reliance on the Steele dossier, but noted it had been received after the initial investigation was opened.

The earlier report had also focused heavily on errors and omitted information found in FBI applications for warrants to eavesdrop on a former Trump campaign aide, Carter Page. The omitted information would likely have weakened or undermined the premise of the application.

Both Durham and the watchdog report did not find any evidence of widespread spying on the Trump election campaign, besides surveillance of Page, one of the main allegations from Trump and his allies.

While the watchdog report called for an array of reforms, with at least 40 ordered by FBI brass in its wake, Durham’s report said further action could be needed.

One idea, he said, would be to identify an official who would be responsible for challenging the steps taken in a probe, in order to provide additional scrutiny of politically sensitive investigations.

How has the FBI responded to Durham’s report?

The FBI has said it has already implemented a series of reforms to address issues with the department’s 2016 probe, including steps meant to ensure the accuracy of secretive surveillance applications.

The department also stressed that the report focused on the FBI’s prior leadership, before current Director Christopher Wray took the job in 2017.

“Had those reforms been in place in 2016, the missteps identified in the report could have been prevented. This report reinforces the importance of ensuring the FBI continues to do its work with the rigor, objectivity, and professionalism the American people deserve and rightly expect,” the FBI said in a statement.

Has anyone been charged in relation to Durham’s probe?

Durham’s report has ended speculation that more people could be charged in relation to the FBI’s Trump-Russia investigation.

Durham previously secured a guilty plea against former FBI lawyer Kevin Clinesmith, who was singled out for altering an email that was used to justify a government wiretap application for Trump aide Page.

His two other cases were less successful. Last year, a jury in Washington, DC, acquitted Clinton’s former campaign lawyer Michael Sussmann on charges he lied to the FBI when he met with the bureau in September 2016 to share a tip about possible communications between Trump’s business and a Russian bank.

Months later, a jury in Virginia acquitted Russian researcher Igor Danchenko of charges that he lied to the FBI.

What are the political implications?

The timing of the report’s release will likely stoke Trump’s narrative that he has been repeatedly targeted by officials in a political “witch hunt”.

Trump has already declared he will run for president in 2024, and while the newest report offered few new revelations, the former president maintained on his Truth Social platform that it showed the “crime of the century”. He further referred to the FBI probe as a Democratic hoax.

Still, the report is likely to only further entrench long-held political narratives.

Tweeting after the report, Republican Congressman Byron Donalds said it showed “Republicans need to rally behind” Trump.

Meanwhile, Democratic Congressman Daniel Goldman, who had previously served as lead counsel in Trump’s first congressional impeachment, called Durham’s report a “political hatchet job”.