Milwaukee, Wisconsin - An exuberant Kamala Harris whipped up a rapturous crowd Tuesday at her first rally since effectively clinching the Democratic presidential nomination, as she launched fresh attacks on Donald Trump for trying to "take the country backward."

In a stark contrast to outgoing President Joe Biden's often stumbling and low-energy speeches, Vice President Harris gave a punchy and enthusiastic address that was greeted with cheers at the event in the battleground state of Wisconsin.

Harris (59) is injecting fresh hope into the Democratic party following 81-year-old Biden's stunning exit from the race after a disastrous debate with Trump fueled fears about his age and mental competency.

"Donald Trump wants to take our country backward," Harris told the crowd in Milwaukee. "Do we want to live in a country of freedom, compassion and rule of law, or a country of chaos, fear and hate?"

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Where Biden used to target Trump as a broad threat to democracy, Harris took a more personal, targeted approach by pointing to her record as a California prosecutor who had dealt with what she said were "predators" and "fraudsters" like the former president and convicted felon.

"So hear me when I say I know Donald Trump's type," she said, echoing comments she made to campaign workers on Monday. "I will proudly put my record against his any day of the week."

Harris notably focused on abortion, accusing Trump of trying to ban the procedure and saying that "we trust women to make decisions about their own bodies and not have their government tell them what to do."

The pumped-up crowd repeatedly chanted "Kam-a-la" during her speech in Milwaukee, the same city where Trump was crowned Republican nominee at his party's conference just last week.

Trump's campaign has been thrown into turmoil after Biden's departure, which now makes him the oldest-ever US presidential candidate. But Trump insisted that Harris would be "easier" to beat in November than her boss.

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Trump, who survived an assassination attempt on July 13, also told reporters he would "absolutely" take part in at least one presidential debate with Harris.

Harris – who is the first female, Black, and South Asian "veep" in US history and aiming to become the country's first woman president – took just 36 hours to secure enough delegates to be nominated after Biden's withdrawal.

Top Democratic congressional chiefs – Senator Chuck Schumer and House minority leader Hakeem Jeffries – threw their weight behind her in a press conference Tuesday.

Hollywood star George Clooney – who made waves earlier this month as one of the first high-profile Democratic activists to urge Biden to drop his reelection bid – also backed her.

A poll released on Tuesday, taken after Biden stepped down, showed Harris two points ahead of Trump.

But Harris has less than four months to prove to US voters that she has what it takes – and she admitted at the Milwaukee rally that there was "hard work" ahead.