In the first moments of his presidency, Joe Biden called on Americans to set aside their deep divisions inflamed by a predecessor he intentionally ignored. He emphasized national unity and appealed to Americans to come together to “end this uncivil war”.

Nearly a year later, as a divided nation reflects on the first anniversary of the 6 January assault on the US Capitol, the uncivil war he sought to extinguish rages on, stronger than ever. In a searing speech on Thursday, Biden struck a different tone.

He said he was “crystal clear” about the dangers facing the nation, and accused Donald Trump and his political allies of holding a “dagger at the throat of America, at American democracy”. In the course of the 21-minute speech, delivered from the US Capitol, Biden offered himself as a defender of democracy in the “battle for the soul of America”.

“I will stand in this breach,” he promised. “I will defend this nation.”

That moment of visceral speech-making marked a shift in strategy for how Biden has chosen to engage Trump – whose name he never uttered but instead taunted as the “defeated former president”.

The decision to break his silence about Trump comes at a challenging moment in Biden’s presidency, with his Build Back Better agenda stalled, the Covid-19 pandemic resurgent and economic malaise widespread. It also reflected the reality that, far from being shunned, Trump remains the most powerful force in the Republican party and a potential rival to Biden in 2024.

Confronting Trump was a calculated risk. Trump seized the opportunity to hurl all manner of insults and accusations at his successor, whose remarks he said were “very hurtful to many people”.

But Biden’s speech was an acknowledgment that there were dangers in continuing to ignore Trump and what Biden called his “web of lies”. Recent polling suggests the vast majority of Republicans believe Trump’s unsubstantiated claims about the election fraud while a growing percentage of Americans are willing to tolerate political violence in some instances.

Republican-controlled states are pursuing a raft of new voting restrictions, motivated in part by the doubts they sowed about the 2020 election results. At the same time, Republicans are passing laws that inject partisanship into the administration of elections and vote-counting while stripping power from and driving power from election officials who resisted pressure to throw out votes or overturn the elections in their state.

“It was essential to be specific about the problem, and the source of the crisis,” said Julian Zelizer, a historian at Princeton University. “Otherwise the vague rhetoric, without agency, that we hear about polarization misses the way in which Trump and the GOP are the source of so much instability.”

But he warned that a speech can only do so much. “Without holding people accountable for January 6 and the campaign against the 2020 election, and without real legislation to protecting voting rights and the electoral process, the ‘dagger at the throat of democracy’ won’t go away.”

In his remarks, Biden argued that protecting voting rights was paramount to safeguarding American democracy. He sought to connect the dots between Trump’s promotion that the 2020 election was tainted by fraud and Republicans’ coordinated effort to “subvert” and undermine the electoral process in states where they control the levers of power.

“Right now, in state after state, new laws are being written – not to protect the vote, but to deny it; not only to suppress the vote, but to subvert it; not to strengthen or protect our democracy, but because the former president lost,” he said.

Biden will follow up on the theme on Tuesday when he delivers another consequential speech on voting rights. In Atlanta, Biden and Vice-President Kamala Harris will call for the passage of two voting rights bills that face daunting odds in the US Senate: the Freedom to Vote Act and the John Lewis Voting Rights Advancement Act.

The issue of voting rights has taken center stage after hopes of passing Biden’s sweeping domestic policy agenda were dashed by the opposition of Senator Joe Manchin, the conservative Democrat from West Virginia. So far Republican opposition has blocked passage of the legislation in the evenly divided chamber, where Democrats lack the 60 votes needed to overcome a filibuster.

Manchin again holds the keys on voting rights legislation, which he broadly supports. But his opposition to eliminating the filibuster has forced Democrats to pursue other avenues such as creating an exception in the rules for certain legislation. The Senate majority leader, Chuck Schumer, said he would schedule a vote on easing the filibuster rules not later than 17 January, which is Martin Luther King Day.

Biden has faced immense pressure from civil rights leaders and voting rights advocates frustrated with his handling of the issue, seen as critical to the president’s legacy. Indeed, a coalition of Georgia-based voting rights groups warned Biden and Harris not to bother coming to the state unless they delivered a concrete plan to move forward, according to the Atlanta Journal-Constitution.

The White House press secretary, Jen Psaki, told reporters this week that Biden planned to stress the “urgent need to pass legislation to protect the constitutional right to vote and the integrity of our elections”.

Spencer Overton, an election law expert and the president of the Joint Center for Political and Economic Studies, hopes Biden will use his bully pulpit to explain why passing federal voting rights legislation is so essential to combatting the lies and conspiracies undermining faith in the nation’s system of government.

“Those lies have real consequences,” said. “Sometimes they’re graphic, as we saw a year ago on 6 January, but sometimes they silently erode democracy by preventing average citizens from participating in our democracy, and exercising their freedom to vote.”

“This is the most important legislation in Congress now,” he added. “There’s just no benefit in waiting. The moment is now.”