Top Democratic leaders have hammered Republican presidential candidate Donald Trump for being an agent of chaos and that his failed policies would take America backwards.

Democrats used their national convention in Chicago on Wednesday to cast the former president as an existential danger and project Vice President Kamala Harris as the best person to lead the nation.

Harris, 59, will take on former president Trump, 78, in the November 5 election.

Former president Bill Clinton in his address to the Democratic National Convention said Trump - a paragon of consistency - is dividing, blaming, and belittling.

“He creates and curates chaos. It's showmanship, but it's not leadership,” he said. On the other hand, he said Harris is the only candidate in this race with the vision, the experience, the temperament and the will.

“Now, how does Donald Trump use his voice? Mostly to talk about himself, his vengeance, vendettas, complaints, and conspiracies. The next time you hear him, don’t count the lies-count the I's. He's like the tenor warming up before the opera: me, me, me, me. Kamala Harris is focused on you,” Clinton said.

House Minority Leader Hakeem Jeffries alleged that Trump was the mastermind of the Republican tax scam, where 83 per cent of the benefits went to the wealthiest one per cent in America.

“Trump failed our country during the COVID-19 pandemic. Trump is a chaos agent who is focused on himself, not the American people. Trump tried to destroy our democracy by lying about the election and inciting a violent mob to attack the Capitol,” he said.

Former House Speaker Nancy Pelosi said January 6th was a perilous moment for the American democracy.

“Never before had a president of the United States so brazenly assaulted the bedrock of our democracy, so gleefully embraced political violence, so willfully betrayed his oath of office,” she said.

“Let us not forget who assaulted democracy on January 6. He (Trump) did. But let us not forget who saved democracy that day. We did,” Pelosi said.

Senator Chris Coons said hate and division are the oxygen of Trump.

“Trump and J D Vance need it to survive in politics. People are saying they are weird. And they are weird. And even worse, they are weak,” he alleged.

New Jersey Senator Cory Booker said Trump betrays the ideals of America.

“He viciously attacks Democrats and Republicans. His put-downs know no shame: John McCain's military service, Nikki Haley's heritage. Women. People with disabilities. Trans people. Our veterans,” he said.

“His is the politics of smear and fear, not inspiration and elevation. He speaks more of American carnage than American compassion, But in America, you can't lead the people if you don't love the people. Our nominees Kamala Harris and Tim Walz bring joy...They're the living dreams of their ancestors,” Booker said.

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