Donald Trump turned back the clock to the darkest elements of his presidency on Saturday with a fiery address that showed the threat to American democracy is far from over.

After a lacklustre start to his campaign, Trump appeared to launch his White House bid in earnest with a vintage display of demagoguery that framed the 2024 election as “the final battle” for America.

The former president, wearing dark suit, white shirt and trademark red tie, also declared war on his own Republican party to the delight of ardent fans in the crowd chanting “Trump! Trump! Trump!” and “USA! USA! USA!”

Opinion polls suggest that Trump’s grip on the party is slipping in the wake of the 6 January 2021, insurrection and a disappointing midterm performance. But he continues to rule supreme at the Conservative Political Action Conference (CPAC), billed as the biggest annual gathering of grassroots conservatives.

Feeding off the energy of a crowd that wore “Make America great again” (Maga) caps, and watched by Brazil’s far-right former president Jair Bolsonaro, Trump returned to the authoritarian language that characterised his political rise seven years ago.

“In 2016, I declared: I am your voice,” he said, speaking for just over 100 minutes from a bright blue and red stage in a cavernous ballroom at the closing speech of the CPAC event in Maryland. “Today, I add: I am your warrior. I am your justice. And for those who have been wronged and betrayed: I am your retribution,” he said.

Trump left office in disgrace after two impeachments and a failed attempt to overturn his defeat by Joe Biden in the 2020 election, culminating in a deadly riot at the US Capitol. He faces an array of criminal investigations yet announced another run for president last November at his Mar-a-Lago estate in Florida.

The subdued launch failed to deter rival Republicans rivals such as Nikki Haley, former ambassador to the UN, who has thrown her hat in the ring. Florida governor Ron DeSantis, seen as the most serious threat to Trump, opted out of CPAC and is instead meeting potential backers in California.

The mood at CPAC, held at a convention centre at the National Harbor in Maryland, was sluggish for much of the week but on Saturday night the 45th president drew by far the biggest and noisiest crowd. “I didn’t know this was a rally, Matt,” Trump said at one point to CPAC impresario Matt Schlapp. “It really is a rally.”

Perhaps stung by critics who say Trump has lost the swagger of his first campaign, Trump seemed determined to tap into supporters’ nostalgia and make the case that, together, they could rekindle the old magic. “For seven years you and I have been engaged in an epic struggle to rescue our country from the people who hate it and want to absolutely destroy it,” he said.

“We are going to finish what we started. We started something that was a miracle. We’re going to complete the mission, we’re going to see this battle through to ultimate victory. We’re going to make America great again.”

As the crowd erupted in cheers and chants of “Four more years!”, Trump cast the upcoming election in Manichean terms, returning to his us-versus-them rhetoric of old.

“With you at my side, we will demolish the deep state. We will expel the war mongers… We will drive out the globalists. We will cast out the communists. We will throw off the political class that hates our country … We will beat the Democrats. We will rout the fake news media. We will expose and appropriately deal with the Rinos [Republicans in name only]. We will evict Joe Biden from the White House. And we will liberate America from these villains and scoundrels once and for all,” he said.

Trump then sent a warning to the party that he has shaped in his own image in an effort to crush dissent. “We had a Republican party that was ruled by freaks, neocons, globalists, open border zealots and fools but we are never going back to the party of Paul Ryan, Karl Rove and Jeb Bush.”

In a zigzagging speech, Trump avoided references to DeSantis but repeatedly turned his fire on Biden. “This is the most dangerous time in our country’s history, and Joe Biden is leading us into oblivion,” he said.

Trump insisted that Russian’s Vladimir Putin decided to invade Ukraine because of the US’s botched withdrawal from Afghanistan in August 2021. “And you’re going to have world war three, by the way. We’re going to have world war three if something doesn’t happen fast. I am the only candidate who can make this promise: I will prevent world war three.”

He made the unlikely boast: “Before I arrive in the Oval Office, I will have the disastrous war between Russia and Ukraine ended… I know what to say.”

Trump threw red meat to the base: additional border wall construction and a massive increase in border patrols to stop the flow of illegal drugs, one day voting with paper ballots, a crackdown on trans rights and gender affirmation surgeries. He repeated his false claim that he won the 2020 election “by a lot” when in fact Biden beat him by 7m votes.

But before a cult-like crowd, Saturday’s event was a warning against Democratic complacency, an indicator that Trump is down but not out and that, just as in 2016, history could take a perilous turn. “We have no choice,” he said in a startling contrast to Biden’s pleas for unity, warning “this is the final battle.”

He concluded: “If we don’t do this, our country will be lost forever.”