WASHINGTON – The first lie – the first one that was a crime, at least – came on the fourth day of Donald Trump’s presidency, in a White House office down the hall from Trump’s own.

That day, a pair of FBI agents came to question Trump’s top national security aide, Mike Flynn, about his dealings with the Russian government. Flynn gave the agents a tour of his new spot in the new administration, interrupted at one point as Trump and some movers walked past discussing where to hang art on the walls. Then Flynn took them back to his corner office and calmly lied to them about conversations with Russia’s ambassador.

Flynn, agents later wrote, “did not parse his words or hesitate.” He simply lied.

The exchange was the start of a remarkable succession of lies over nearly two years by some of Trump’s closest political associates, told to federal agents, Congress and the public that distanced the president and his campaign from an investigation into whether his campaign participated in Russian efforts to disrupt the election that put him in office.

Whatever else special counsel Robert Mueller’s now-concluded investigation may reveal, it has devoted considerable attention to the Trump associates whose lies to lawmakers and investigators deflected attention from connections between Russia and the president’s campaign, and to a central question hanging over many of the charges Mueller has filed: Why did they lie?

Mueller delivered his final report Friday to Attorney General William Barr, marking the end of an investigation that has loomed over the first two years of Trump's presidency. The Justice Department has so far revealed none of the report's conclusions, but over the past year and a half, prosecutors have sketched some of them in hundreds of pages of court filings.

Prosecutors have revealed that Trump’s campaign worked eagerly to benefit from a Russian intelligence operation that hacked his opponents’ emails and echoed them in phony social media campaigns, an effort the U.S. government later concluded was aimed in part at helping to deliver Trump the presidency. And investigators charged that a succession of top aides then lied to pretend they hadn’t.

Barr's Letter:Read Attorney General Barr's letter to Congress announcing end of Mueller's Russia probe

Investigation Ends:Special counsel Robert Mueller delivers report marking end of investigation into Trump's campaign, Russia

Mueller’s office accused seven people, all but one of them former aides or advisers to Trump, with making dozens of false statements during the Russia investigation.

The investigation has produced a deluge of falsehoods on subjects from the president’s business dealings in Moscow to a meeting his son and campaign chief attended in Trump Tower in 2016 with a Russian promising “dirt” on his political opponent. But lying to the public is usually not a crime, and Mueller’s investigators zeroed in on those directed to lawmakers and federal investigators.

Trump’s lawyers maintain that the lies reflect little more than a misguided impulse to protect themselves from things that weren’t crimes to begin with. “The thing about all these lies is that if they all just told the damn truth they probably wouldn’t have been in any trouble,” said Rudy Giuliani, Trump’s lead attorney.

Prosecutors haven’t hinted at their answer, other than to reveal that it is one of the subjects they investigated.

But some of the people they have accused of lying have supplied answers of their own: One suggested he lied out of loyalty. Others appear to have been protecting the president. One, Michael Cohen, a former executive in Trump’s private business and his personal lawyer, said he lied because the president wanted him to.

“Everybody's job at the Trump Organization is to protect Mr. Trump. Every day most of us knew we were coming in and we were going to lie for him on something and that became the norm,” Cohen said in sworn testimony to a House committee Feb. 27. “And that's exactly what's happening right now in this country and it's exactly what's happening here in government.”

23 months of Russia lies

Flynn has pleaded guilty to lying to the FBI on Jan. 24, 2017, about conversations with Russia’s ambassador, including one in which he discussed rolling back sanctions the Obama administration had imposed in response to Moscow’s election-meddling.

Three days after that meeting, two FBI agents went looking for a young campaign aide, George Papadopoulos. They took him from his mother’s house in Chicago to the bureau’s office there, switched on a video camera, and warned him to tell the truth.

“The only way you’re getting in trouble today is if you lie to us,” one said, according to court records.

For two hours, the agents quizzed Papadopoulos on his interactions with a professor in London named Joseph Mifsud and other people Papadopoulos believed had ties to the Russian government. Eventually, Papadopoulos revealed that Mifsud told him in early 2016 that Moscow had gathered “dirt” on Hillary Clinton, in the form of “thousands of emails,” months before the government revealed that Russia’s military intelligence service had hacked Democratic political organizations. But Papadopoulos passed his encounter with Mifsud off as a “strange coincidence,” unrelated to his work for Trump.

He later admitted that wasn’t true; Mifsud approached him because of his role on the campaign.

More lies by Trump associates followed.

That August, Michael Cohen lied in a written statement to two congressional committees about Trump’s efforts to construct a potentially lucrative high-rise in Moscow, telling them that they ended early in the campaign, when in fact those efforts continued until the point – almost six months later – when Trump had effectively secured the Republican presidential nomination. Cohen also tried to mislead members of Congress into thinking that Trump himself was uninvolved in the project.

A month after that, in September 2017, prosecutors allege that another Trump confidante, Roger Stone, lied to lawmakers about his efforts to gather information for the campaign about hacked emails that were being released by the anti-secrecy group WikiLeaks. Prosecutors said someone in Trump’s campaign directed a senior campaign official to get in touch with Stone about any other “damaging information” the group might have on Clinton.

When lawmakers summoned one of Stone’s associates to testify, Stone suggested he, too, stick to the story, saying in a text message obtained by prosecutors: “Stonewall it. Plead the fifth. Anything to save the plan’ … Richard Nixon.”

Cohen, Flynn and Papadopoulos have pleaded guilty to making false statements. So has Manafort’s former deputy Rick Gates, and an attorney who worked with the pair, Alexander Van Der Zwaan. Stone, who has maintained his innocence, is scheduled to go on trial in November on charges of lying to Congress and obstruction of justice.

Late last year, Paul Manafort, the former chairman of Trump’s campaign, met with investigators and appeared twice before a grand jury. There, prosecutors alleged in court filings, he lied about his interactions with a business associate in Ukraine who U.S. authorities say is tied to Russian intelligence. Prosecutors say Manafort passed polling data to the foreign associate while running Trump’s campaign.

Prosecutors didn’t charge Manafort with lying, though a judge concluded that he had. Instead they sought to use his lies against him when he was sentenced for other crimes, including conspiracy and tax and bank fraud related to years of lobbying work he conducted in Ukraine.

The full consequence of all the lies remains to be seen.

The personal legal jeopardy for Trump’s associates is playing out in courtrooms from New York to Washington. It’s less clear the implications those lies have had on Mueller’s effort to understand the scope of the Russian government’s intelligence operation around the 2016 election, and how directly it was able to tap into Trump’s campaign, if at all.

David Laufman, who ran the Justice Department’s counter-intelligence unit from 2014 until early 2018, declined to comment on the cases Mueller filed, but said the urgency of finding and countering foreign intelligence operations should be obvious.

“It’s essential when a counterintelligence threat is discovered for the FBI and the Justice Department to be able to take appropriate investigative steps to get to the heart of the matter as quickly as possible,” he said. “If someone the FBI goes to interview is withholding information from the government, that’s a serious matter."

'Loyalty' and 'orders'

Trump has tried repeatedly to discredit Mueller’s investigation, savaging it as a political “witch hunt.” The FBI has confirmed that it investigated whether the president also tried to obstruct it, and Mueller’s office closely scrutinized the false statements of Trump aides.

Both Cohen and Flynn have agreed to cooperate with prosecutors and have provided information about the circumstances in which they lied.

“The obvious question on the obstruction theory is who, if anyone, is suggesting that they’d want to cover it up,” said Shanlon Wu, a former federal prosecutor who represented Gates until last year.

“Isn’t it a remarkable coincidence — why are they all lying?” said Robert Ray, a former independent counsel who investigated President Bill Clinton. “Politics is one of those spaces where loyalty is prized above most everything,” Ray said. “When you look at these cases, it’s like everyone understood that — down to the lowest staffer.”

Flynn has never revealed why he lied, and it’s puzzled those who know him.

Giuliani said it was “stupid perjury,” because Flynn, the former head of the Defense Intelligence Agency and a retired general, should have known the government was monitoring his contacts with Russia’s ambassador. Giuliani also said it was “outrageous” that agents questioned Flynn without a lawyer and didn’t give him a chance to correct his false statements.

Robert “Rocky” Kempenaar, one of Flynn’s longtime friends from Rhode Island, said he believes he lied to protect the president and his administration and that he did not decide to do it on his own.

“He’s a general,” Kempenaar said. “He was following orders from above him. Whether it was the president, I don’t know, but I kind of figured it out knowing Michael the way we do.”

Cohen, too, placed Trump squarely at the center of the obstruction investigation. In scathing testimony to the House Oversight Committee in early February, he said Trump had implicitly encouraged him to lie to lawmakers about plans to build a Trump Tower in Russia. And he testified that some of Trump’s lawyers reviewed and edited a false written statement before he delivered it to Congress in 2017.

“Mr. Trump did not directly tell me to lie to Congress, that's not how he operates,” Cohen said. “In conversations we had during the campaign, at the same time I was actively negotiating in Russia for him, he would look me in the eye and tell me, there's no Russian business, and then go on to lie to the American people by saying the same thing.

“In his way, he was telling me to lie.”

Cohen has not said when or where he had those conversations with Trump, but investigators revealed in warrant applications that they had extensively monitored both his communications and his location. He submitted documents to the House Intelligence Committee about his interactions with Trump's lawyers.

Prosecutors have so far offered nothing to substantiate that account, though they confirmed to a judge last year that Cohen had given them information about the “circumstances of preparing and circulating,” his written statement to Congress, which they found both “relevant and truthful.”

Beyond that, Mueller’s office has offered only brief explanations for why they think Trump’s aides lied.

One of its top prosecutors, Andrew Weissmann, told a judge last year that the special counsel’s office thought Manafort had lied to investigators – after promising to cooperate – to “augment his chances for a pardon.”

And they said Papadopoulos was seeking a job with Trump’s National Security Council or elsewhere in the administration when he lied to the FBI, telling agents he was “trying to help the country and you guys, but I don’t want to jeopardize my career.”

Papadopoulos' lawyer offered a clearer explanation last year before the former foreign policy aide was sentenced to 14 days in prison. He lied, Thomas Breen said, out of “misguided loyalty to his master.”

Contributing: Bart Jansen