WASHINGTON (AP) — The Justice Department's internal watchdog released a report that found the FBI had a legitimate reason to open up one of the most politically sensitive investigations ever, the Russia probe that began in secret during Donald Trump's 2016 presidential campaign that eventually was taken over by special counsel Robert Mueller. But the report, issued Monday, also documented errors during the investigation that Trump and his supporters could seize on as vindication. It had been highly anticipated, in Washington anyway, but the conclusions were nuanced — and as so many other key moments over the past few years — that made it difficult for any side to claim total absolution.

Some key takeaways:

SUPPORTING THE FBI:

The report found the FBI was justified in its opening of an investigation into ties between the Trump presidential campaign and Russia — to protect against a national security threat. It also found the bureau didn't act with political bias despite Trump's constant claim that it was a political "witch hunt" and Republicans bashing the storied investigative agency as biased. And the FBI was justified in obtaining a warrant from the secretive Foreign Intelligence Surveillance Court to eavesdrop on former Trump campaign adviser Carter Page. Subsequent warrant renewals were also OK.

Democrats quickly touted the importance of the report. U.S. Sen. Charles Schumer, a New York Democrat and minority leader, said the report should serve as a wake up call and reiterates the conclusions of the intelligence community. "Our country would be better served if President Trump, AG Barr, Republicans in Congress, and their supporters stopped pushing baseless conspiracy theories and instead worked in a bipartisan fashion to ensure the FBI and the Intelligence Community have the full support and resources necessary to stop Putin and any other foreign adversary from interfering in the 2020 elections."

SUPPORT FOR TRUMP:

Trump said in remarks at the White House shortly after the report's release, that it showed "an attempted overthrow and a lot of people were in on it." It wasn't quite that, but it did reveal problems.

The inspector general identified 17 "significant inaccuracies or omissions" in applications for the warrant to monitor Page's communications. The errors resulted in "applications that made it appear that the information supporting probable cause was stronger than was actually the case."

While the report made clear that a frequent Republican target, former British spy Christopher Steele, had nothing to do with the start of the probe, the report was critical about how information from Steele was used to get a warrant on Page. The FBI didn't disclose that Steele's work was being financed by the Democrats and the Clinton campaign. The report faulted the FBI for failing to update the Foreign Intelligence Surveillance Court as it learned critical new facts about Steele and his connections, including the fact that the political research firm that relied on him to dig into Trump was hired by Democrats.

THE TRUMP CAMPAIGN REALLY WAS SPIED ON

The report details how the FBI had an informant reach out to a high-level Trump campaign official. The source set up a meeting in September 2016 and then recorded the conversation with the official, who was not a subject of the Russia investigation. The campaign official isn't identified by name. The inspector general found no evidence that the information collected by the informant was used in the Russia investigation.

There is no evidence in the inspector general's report that surveillance was unlawful. But it makes clear that Trump and Barr were correct when they said the Trump campaign was spied upon. Barr said during a congressional appearance in April that "spying did occur" on the campaign and Trump has taken it a step further, repeatedly accusing the government of committing an illegal, unprecedented act.

A CHILLY RECEPTION:

Trump's Justice Department made clear they are not accepting the watchdog report as the last word. Attorney General William Barr and U.S. Attorney John Durham, who is conducting a criminal investigation into the origins of the Russia probe, both rejected the inspector general's finding that there was sufficient evidence to open the investigation. Barr said in a statement that the report made clear the FBI launched an "intrusive investigation" into the Trump campaign based on "the thinnest of suspicions that, in my view, were insufficient to justify the steps taken."

Durham informed the inspector general that he also doesn't agree with the conclusion that the inquiry was properly opened, he said in a statement. He suggested his own investigation would back up that assertion. Last week, Trump suggested that Americans should really be more interested in Durham's findings, which he referred to as the "big report."

HOW DOES THIS FIT INTO THE IMPEACHMENT INQUIRY?

The report came the same day as a House Judiciary Committee impeachment hearing centered on the president's interactions with Ukraine. It was the latest affirmation that Russia, not Ukraine, interfered in 2016, as intelligence communities have said, and some Republicans have disputed. The report gives credibility to the Russia investigation. Meanwhile, Republicans argue the impeachment inquiry, centered on the president's July 25 call with the newly-elected leader of Ukraine is just another attempt to corner Trump by Democrats, after their first attempt — the Russia probe — failed. Part of Trump's conversation with Ukrainian president Volodymyr Zelenskiy was a request that the new president look into a debunked theory that Ukraine had meddled in the 2016 election. He also wanted Zelenskiy to investigate the family of political rival, Democrat Joe Biden.

A NEW PROBE OPENED

The inspector general has launched another investigation looking at the FBI's procedures for using secret surveillance warrants under the Foreign Intelligence Surveillance Act because of "extensive compliance failures" that were uncovered during the investigation. That law, known as FISA, allows the government to conduct surveillance in some of the most sensitive FBI investigations. The watchdog concluded there were not only failures by the team directly involved in the investigation into election interference and possible coordination with the Trump campaign, but also found systemic issues extending to supervisors and managers in the FBI's chain of command. The report recommends the FBI conduct its own review of the preparations for FISA warrants. The inspector general's audit will look at whether the FBI is properly following its own protocols to obtain FISA applications in both counterintelligence and counterterrorism investigations.

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Associated Press writer Mary Clare Jalonick contributed to this report.