US Vice-President Kamala Harris has gone on the offensive against Donald Trump in the first rally of her White House campaign, portraying November’s election as one between a former prosecutor and a convicted felon.

Speaking to a crowd of thousands in the battleground state of Wisconsin, Ms Harris likened her Republican opponent to fraudsters she said she had prosecuted.

Trump, meanwhile, assailed her work on the border, and posted on social media: “Lyin’ Kamala Harris destroys everything she touches!”

It comes a day after she secured the support of a majority of Democratic delegates, paving the way for her to become the party’s nominee.

On Sunday afternoon, President Joe Biden announced he was withdrawing from the race and endorsed his vice-president amid mounting pressure from top Democrats and donors following his disastrous debate against Trump in late June.

The fledgling Harris campaign raised a staggering $100m plus (£77m) in the 36 hours after Mr Biden’s exit.

Adding to her momentum, a new national poll from Reuters and Ipsos shows her with a two-point lead over Trump, 44% to 42%.

Taking the stage to applause at a high school in Milwaukee on Tuesday, Ms Harris highlighted her experience as California’s attorney general.

“I took on perpetrators of all kinds,” she said. “Predators who abused women. Fraudsters who ripped off consumers. Cheaters who broke the rules for their own gain.”

“So hear me when I say I know Donald Trump’s type,” Ms Harris added. “In this campaign, I promise you, I will proudly put my record against his any day of the week.”

In response, the crowd shouted “Kamala! Kamala!” Some observers noted that the audience’s enthusiasm contrasted with that seen at Biden events this electoral cycle.

Trump, meanwhile, posted on his social media platform, Truth Social, about a poll finding that Ms Harris was the most unpopular vice-president in US history.

He also shared a post noting that she was rated by the non-partisan congressional scorekeeper GovTrack as one of the most left-wing among dozens of Democratic senators during her tenure.

Ms Harris laid out a number of policy priorities in her speech, including tackling child poverty, union rights, affordable healthcare and being able to “retire with dignity”.

She also focused on gun control and abortion access, vowing to stop Trump’s “extreme abortion bans, because we must trust women to make decisions about their own body”.

The Republican party platform, approved by Trump, does not advocate for any abortion restrictions at the federal level, instead leaving the matter up to individual US states to decide.

The Trump campaign is focusing on Ms Harris’ “failure” to stem a record influx of illegal immigrants at the US-Mexico border.

A Tuesday afternoon email from the Republican nominee’s team accused her of bailing out “accused murderers, rapists and other violent offenders”, insulting Israel and deceiving the US public about Mr Biden’s “cognitive decline”.

During a call with reporters, Trump said of Ms Harris: “She’s a radical left person, but this country doesn’t want a radical left person to destroy it.

“I think she should be easier than Biden, because he was slightly more mainstream, but not much.”

Trump also said he was open to debating her in September, when he was originally due to face Biden on ABC News.

“I haven’t agreed to anything,” he said. “I agreed to a debate with Joe Biden. But I want to debate her. She’ll be no different.”

In Washington, a Republican member of the US House of Representatives introduced articles of impeachment against Ms Harris.

The resolution, written by Tennessee’s Andy Ogles, accuses her of high crimes and misdemeanours over her handling of immigration at the border.

It is considered unlikely to advance.