Originally Published: 05 JAN 22 18:00 ET

Updated: 06 JAN 22 10:16 ET

By Kevin Liptak and Jeff Zeleny, CNN

(CNN) -- Two weeks before becoming president, Joe Biden watched the January 6 attack on television from his home in Delaware, horrified as the unspeakable images of the insurrection unfolded and aghast at the sitting President's unwillingness to condemn it.

A year later, he marked that day with a speech that put into stark terms what the event meant for a nation still deeply split over its significance -- and excoriating his predecessor for his role in eroding American democracy.

In his speech from the Capitol's Statuary Hall on Thursday, the President wielded the sharpest language he's ever used about the attempted coup, denouncing "the former President" 16 times for lying about the election because he couldn't reckon with losing.

"He's not just a former President," Biden said in his forceful remarks, "he's a defeated former President."

Biden touched upon his deeply personal views of the assault on democracy and the attack on the hallowed Capitol building where he spent nearly four decades during his time as a senator.

But he also acknowledged it wasn't a battle he necessarily expected or sought.

"I did not seek this fight, brought to this Capitol one year ago today," he said. "But I will not shrink from it either. I will stand in this breach, I will defend this nation, I will allow no one to place a dagger at the throat of democracy."

Biden worked over the holidays to write and refine an address that was bluntly honest about the motivations and consequences of the riot, along with the threats to American democracy that still persist. It's a topic that drives Biden, according to officials, but one that hasn't played a central role in his public agenda. He has left investigating the riot to Congress and made clear he won't interject into the Justice Department's prosecution of its perpetrators.

Still, the January 6 riot has doggedly shadowed Biden's first year in office. The insurrection was unsuccessful in preventing him from becoming president, but it has instead become a persistent reminder of the divisions he once promised to heal and the fraught political environment in which he governs.

Biden has made attempts to bridge those divisions by doing what he can to move on. Even as many Democrats warn of troubling steps taken around the country that could potentially undermine future elections -- including installing loyalists to Donald Trump on election boards and changing local voting laws -- the President spent his first year in office prioritizing other legislative battles, including Covid relief money, an infrastructure bill and a large social and climate spending package that is still pending.

Mindful of not allowing Trump to hijack his presidency, Biden has made it a habit not to mention his predecessor by name, though he still does sometimes. He recently claimed, "I don't think about the former President."

Yet Trump's influence has persisted, including in Congress where January 6 has become an enduring test of loyalty to the former President. While Trump canceled a news conference scheduled for Thursday at his Mar-a-Lago resort in Florida, he continues to spread false information about the election at rallies and during media appearances.

Trump's false claims about the election and the riot continue to undermine Biden among Republicans around the country. This week, an NPR/Ipsos poll found two-thirds of Republicans agree that fraud helped Biden win -- a claim that has repeatedly been discredited.

'We have much to do'

One year ago on that January afternoon, Biden was two weeks away from being sworn in as president and was scheduled to give a speech on the economy. Those remarks were delayed for more than two hours as a paralyzed nation viewed the violence with horror and disbelief.

That day, Biden told one of his closest aides that his transition to power -- and likely his presidency -- had just become markedly more difficult.

It was a rare exception during his two months as president-elect when Biden directly raised Trump's name during a public speech, demanding he call off his loyal followers.

"At this hour, our democracy's under unprecedented assault, unlike anything we've seen in modern times. An assault on the citadel of liberty, the Capitol itself," Biden said, before imploring Trump "to fulfill his oath and defend the Constitution and demand an end to this siege."

Fourteen days later in his inaugural address, delivered from the very spot of the rampage, Biden sought to use the deadly riot as a teachable moment for the nation, striking an optimistic note that a divided nation could come together.

"We have much to do in this winter of peril and possibility," Biden said. "Much to repair, much to restore, much to heal."

On that day, memories of the Capitol breach were still fresh among the lawmakers and other officials who gathered on West Front. At the time, nerves in Washington were raw from the violence, razor-topped fencing surrounded the Capitol complex and 25,000 National Guardsmen were patrolling the city as fears of more violence persisted.

Since that moment, though, the lie undermining Biden's victory over Trump has grown beyond any expectation. The anniversary speech that Biden delivered on Thursday was far more pointed.

"For the first time in our history, a president not just lost an election, he tried to prevent the peaceful transfer of power as a violent mob breached the Capitol," Biden said, repeatedly using some of the words Trump is known to dislike -- "lost," "defeated" and "failed: -- to deliver a blistering attack on his predecessor.

"We must be absolutely clear about what is true and what is a lie. Here's the truth," Biden said. "The former President of the United States of America has spread a web of lies about the 2020 election."

Asked as he was departing the Capitol Building why he did not use Trump's name, Biden said he was aiming for something larger.

"I did not want to turn it into a contemporary political battle between me and the President," he said. "It's way beyond that."

A day that won't go away

As Biden nears the one-year mark of his presidency, the change in tone underscores one of the biggest surprises of the office: Trump, whom he defeated 306 to 232 electoral votes, looms far larger than the predecessor of any modern-day president.

The opening weeks of Biden's presidency shared a spotlight with Trump's second impeachment trial in the Senate, where the Republican was ultimately acquitted after Democrats accused him of inciting the riot at the Capitol.

In other ways, January 6 has continued to arise at regular intervals. The event has seeped into his diplomatic conversations. Biden has cited fellow world leaders who he says ask him regularly whether American democracy will survive its current strains: "Is America going to be all right?" he claims his counterparts ask him at foreign summits and over the phone.

When lawmakers were in the process of forming a committee to investigate the attack in the spring, Biden voiced support for the efforts but otherwise sought to put distance between himself and the process, insisting the decisions on the panel's makeup and mission were best left to members of Congress.

Biden and his team have generally rejected Trump's claims that all internal White House documents should be shielded by executive privilege. They have argued in legal letters it is "not in the best interests of the United States" for Trump's claims of executive privilege to stand.

Yet White House lawyers have also sought to keep a certain number of records the committee has requested from becoming public, arguing their release could harm national security. Those records had been the subject of negotiations between the top White House lawyer and the committee and were an indication of the inherent tension between two different branches of government.

Biden himself has weighed in only sporadically on the proceedings. After saying in October that he thought the Justice Department should prosecute former Trump aide Steve Bannon for failing to comply with a committee subpoena, Biden said it was not appropriate for him to have voiced his opinion.

Last month, he said former Trump chief of staff Mark Meadows was "worthy of being held in contempt" for similarly failing to appear for a deposition.

Behind the scenes, Biden has been kept abreast of the committee's work but isn't focused intensely on it, according to aides. He has placed greater importance on strengthening voter protections and ensuring future elections aren't subject to false challenges.

Democrats are looking to use the January 6 anniversary as a launching point to advance voting rights legislation, which has been stalled for the past year. Activists are pushing for Biden to reorient his strategy in the new year to pass something by the Martin Luther King Jr. holiday in mid-January. Doing so would likely require altering Senate rules to overcome Republican opposition.

White House officials say Biden will touch on voting rights in his speech Thursday, but intends to address the topic in a far more substantive way next week during a trip to Atlanta, the cradle of the civil rights movement. He and Vice President Kamala Harris are set to visit Georgia on Tuesday.