WASHINGTON (AP) — The fear was persistent. As the Russia investigation heated up and threatened to shadow Donald Trump's presidency, he became increasingly concerned. But the portrait painted by special counsel Robert Mueller is not of a president who believed he or anyone on his campaign colluded with Russians to interfere in the 2016 election.

Instead, the Trump of the Mueller report is gripped by fear that Americans would question the very legitimacy of his presidency. Would Trump, the man who put his name on skyscrapers and his imprint on television, be perceived as a cheater and a fraud?

To Trump, his victory over Hillary Clinton was both historic and overwhelming, though he won millions of votes less than did the Democratic candidate.

If people thought he'd won with the help of Russia, that glorious victory might be tainted.

Just a month after Election Day, on Dec. 10, 2016, reports surfaced that U.S. intelligence officials had concluded Russia interfered in the election and tried to boost Trump's presidential bid.

The next day, Trump went on Fox News and called the assessment "ridiculous" and "just another excuse." The intelligence community actually had "no idea if it's Russia or China or somebody," he argued.

"It could be somebody sitting in a bed some place," the Republican president-elect added.

The president's public narrative quickly shifted. He blamed Democrats and accused his political opponents of putting the story out because they "suffered one of the greatest defeats in the history of politics."

But the intelligence community's assessment that Russia had interfered in the 2016 election to sow discord among American voters and to help get Trump elected was his "Achilles' heel," one of his closest aides, Hope Hicks, would tell investigators.

In the months that followed, Trump reacted strenuously to investigations into links between the Russians and his campaign and transition teams.

Michael Flynn, who served on the transition team and would go on to be national security adviser, spoke with Sergey Kislyak, Russia's ambassador to the U.S. Flynn asked that Russia not retaliate against the United States because of sanctions announced by the Obama administration; the ambassador later told Flynn that Russia would hold back.

In the weeks that followed, Trump paid careful attention to what he saw as negative stories about Flynn. He grew increasingly angry when a story broke pointing out that Flynn had discussed sanctions with Kislyak.

By mid-February, Flynn was forced to resign.

A day later, as Trump was set to meet with FBI Director James Comey, the president had lunch with his confidant and former New Jersey Gov. Chris Christie. He told Christie he believed the Russia investigation would end because of Flynn's departure.

"Flynn met with the Russians. That was the problem. I fired Flynn. It's over," Trump said.

That couldn't have been further from the truth.

The fear — and Trump's anger — continued for months as the Russia investigation ensnared some of his closest confidants. Over and over, he would tell advisers that he thought the public narrative about Russian election interference was created to undermine his win. It was a personal attack, he insisted.

On May 9, 2017, Trump fired Comey. Trump would later admit in an interview that he had considered "this Russia thing" when he decided to fire Comey.

Days later, Trump held an Oval Office meeting with Attorney General Jeff Sessions, White House lawyer Don McGahn and Sessions' chief of staff Jody Hunt to interview candidates to be the next FBI director.

Sessions walked out of the room to take a call from his deputy attorney general, Rod Rosenstein. When he returned, he informed Trump that Rosenstein had appointed a special counsel to investigate possible coordination between the Trump campaign and Russia.

Trump feared that his presidency, still in its infancy, could be over. And he was furious his aides hadn't protected him.

The president slumped back in his chair.

"Oh my God. This is terrible. This is the end of my Presidency. I'm f---ed. This is the worst thing that ever happened to me," he said.

For months, as the Russia investigation grew and more people in Trump's inner circle appeared to be under intense scrutiny from federal investigators, Trump became completely preoccupied with press coverage of the probe. The message was persistent: It raises questions about the legitimacy of the election.

At rallies and on Twitter, Trump decried what he said was a politically motivated "witch hunt."

In the end, the redacted version of Mueller's report cleared the Trump campaign of colluding with Russian efforts to influence the election.

Trump crowed that the report found "No Collusion." But he ignored Mueller's finding that Russian meddling was very real and was intended to support Trump's campaign.

Did Russia's efforts lead to Trump's victory? Mueller doesn't venture an opinion, much as he does not decide whether Trump committed obstruction of justice.

But how could Trump have obstructed justice if there was no collusion to hide?

The lack of an underlying crime doesn't really matter, Mueller contended. Trump still had a motivation to obstruct the investigation — the fear that people would question the legitimacy of his election.