They lied to the public for months before Donald Trump was elected – and then repeatedly after he took office.

They lied to Congress as lawmakers sought to investigate Russia’s attack on American democracy in 2016.

And they lied to the FBI, even when they knew lying was a crime.

In indictments and plea agreements unveiled over the last 20 months, special counsel Robert Mueller III has shown over and over again that some of President Trump’s closest friends and advisers have lied about Russia and related issues.

On Friday, Mueller laid out a new allegation: that longtime Trump confidant Roger Stone lied to Congress and obstructed its probe of Russia’s interference in the 2016 campaign.

Trump and his associates have dismissed the serial deception as a sideshow that has little to do with the central question of the Mueller investigation: whether his campaign engaged in a criminal conspiracy with Russia.

Following Stone’s indictment on Friday, Trump attorney Rudy Giuliani scoffed, “Another false-statement case? God almighty.”

But it is unclear if the special counsel shares that view. While Mueller has not accused any American of criminally coordinating with Russia, the lies meticulously unspooled by his prosecutors over 20 months have not been mere quibbles.

They have documented various falsehoods by Trump advisers that masked efforts by people in his orbit to develop inroads with Russia and leverage that country’s hacking of Democratic emails.

The remaining question – for both Mueller’s team, as it works on a final investigative report, and for the American people – is why.

Did the president’s men lie to protect a still-hidden dark secret about the campaign’s interaction with Russia, engaging in a broad effort to obstruct the probe – one that included perhaps even Trump?

Did they lie to avoid diminishing Trump’s victory by acknowledging Russia played a role in his election?

Did they each lie for their own reasons, taking their cue from the president – who has told many whoppers of his own, including about Russia?

Trump’s former campaign chairman, deputy campaign manager, former national security adviser, personal lawyer and a campaign foreign policy adviser have all been accused of lying to investigators exploring Russia activity.

In their new indictment against Stone, prosecutors said he lied to Congress about his efforts to learn about WikiLeaks’s plans in 2016 as the group was publishing Democratic emails allegedly stolen by Russian operatives.

Stone falsely told Congress that he never discussed his efforts with the Trump campaign and never asked intermediaries to communicate with WikiLeaks’ founder, Julian Assange, Mueller’s team alleges.

Stone has denied the charges and promised to fight in court. “Perjury requires both materiality and intent,” he said on CNN Friday night. “There is none.”

“Secondarily, where’s the Russian collusion?” Stone added. “Where is the WikiLeaks collaboration? Where’s the evidence that I received anything from WikiLeaks or Julian Assange, and passed it on to Donald Trump or the Trump campaign?”

Trump echoed that message himself.

“Greatest Witch Hunt in the History of our Country! NO COLLUSION!” the president tweeted after Stone’s arrest.

Legal experts noted that the alleged lies are significant in their own right.

“Time and time again, elected officials and government officials have exhibited a belief they simply can say what they want in a high-profile investigation, and do so with impunity,” said Jacob S. Frenkel, a former attorney in the independent counsel’s office now in private practice at Dickinson Wright.

Some Trump friends said they are confounded by Stone’s alleged actions.

“If he had told the truth as alleged, there wouldn’t have been an underlying crime,” said Christopher Ruddy, chief executive of Newsmax. “There would have been no crime. They would have had to try and find other stuff.”

The Stone indictment does provide new details that nod at one of Mueller’s central inquiries: trying to determine whether anyone in Trump’s orbit coordinated with Russia or WikiLeaks.

In Friday’s filing, prosecutors lay out efforts by both Stone and Trump campaign officials to learn more about what WikiLeaks had in its cache in the summer of 2016 – actions that occurred after Russia had been fingered as a likely culprit behind the theft of the Democratic Party emails that June.

Still, the mounting false statements charges collected by Mueller do not speak to the question of criminal coordination between the Trump campaign and Russia, some analysts noted.

“I think there is some theory under which you could include them in such a conspiracy, and I wonder why not,” said Barbara McQuade, a former U.S. attorney. “Is it that they don’t think the evidence goes that far? Is it that they think this conduct does not amount to a conspiracy to defraud the United States and it is instead dirty, political tricks?”

Steve Hall, who retired from the CIA in 2015 after 30 years of running and managing Russia operations, said that the substance of the lies and alleged false statements documented by Mueller paint a broad picture with serious implications.

“In my view, those lies – what was lied about and under what condition the lies were told – contribute to a counterintelligence pattern that has begun to emerge pointing to senior members of the Trump team being involved with the Russians,” he said.

Hall said the country needs to take step back from a narrow conversation about the political and even criminal ramifications of each Mueller indictment. “We’ve got to be looking beyond who gets a parking ticket or even a few years in prison,” he said. “What about the bigger picture? This was Russia, attacking the United States.”

The deception by Trump advisers that has led to guilty pleas so far does have a common throughline: Much of it centers on their interactions about Russia.

Trump’s longtime personal attorney Michael Cohen admitted lying to Congress about efforts to build a Trump real estate project in Moscow during the campaign – at a time when then-candidate Trump claimed he had no business ties to Russia.

Michael Cohen, the president’s former personal attorney, admitted to lying to Congress, among other charges. He is expected to testify again before the House Oversight Committee and has been subpoenaed to testify before the Senate Intelligence Committee.

Cohen also lied about seeking help on the lucrative project from one of Russian President Vladimir Putin’s closest advisers. Trump had said no one in his orbit had contact with the Russian government.

Former national security adviser Michael Flynn admitted he lied – first to Vice President Mike Pence, then to the public and finally to the FBI – about whether he had spoken to a Russian envoy in December 2016 about sanctions imposed by President Barack Obama as punishment for Russia’s campaign interference.

That lie came as investigators were working to understand why Russia, whose top foreign policy goals include undoing U.S. sanctions, fought so hard to help elect Trump over Democrat Hillary Clinton.

Foreign policy adviser George Papadopoulos has admitted lying about his contacts with a professor who gave him early warning in April 2016 that Russia held thousands of Clinton emails.

Prosecutors have said former Trump campaign chairman Paul Manafort has continued to lie even after pleading guilty to two conspiracy charges, which included lying to the Justice Department. His latest lies, they have said, involved details of his campaign interactions with a Russian employee who the FBI has assessed has ties to Russian intelligence.

As they wait for Mueller to finish his investigation, Democrats in Congress are likely to focus on the president himself and what he knew of the lies.

On Friday, Rep. Jerrold Nadler, D-N.Y., the chairman of the House Judiciary Committee, tweeted: “Roger Stone, Paul Manafort, Michael Cohen, Rick Gates, Michael Flynn … What did the President know and when did he know it?

Some legal analysts said the charges do not appear to be building to a criminal case against the president.

The lying “certainly alerts you to the possibility of kind of obstructionist conspiracies,” said James M. Trusty, a former Justice Department organized crime chief now in private practice at Ifrah Law. But, he added, “at the end of the day, it looks like people are making independent, individual choices that are landing them in hot water. I think it’s the kind of thing that the Mueller probe doesn’t want to ignore … but the indictments themselves aren’t moving the case forward.”

The number of lies documented by the special counsel could also undercut Mueller’s efforts to make a broader case by hampering the effort to sort truth from fiction, some longtime Trump associates said.

“In Trump world, everybody lies. Everybody doesn’t tell the truth. At the end of the day, they are all lying. I don’t know how Mueller can believe anybody,” said Louise Sunshine, a longtime executive with the Trump Organization.

Trump allies say the president knows that many of the people around him are not trustworthy – and believes he can use that to his advantage if any of his onetime aides attempt to pin their wrongdoing on him.

He has instructed Giuliani and his other lawyers to question the credibility of anyone who attacks him, according to White House aides who spoke on the condition of anonymity to describe private conversations. After Cohen, Trump’s longtime personal attorney, pleaded guilty, the president on Twitter called him a “rat” who “makes up stories.”

Sam Nunberg, a former Trump aide, said he believed that people around Trump lied to investigators because they were trying to make sure their version of events lined up with lies the president was telling to the American people.

“They all conspired,” he said, “against themselves.”