Speaking after his wife Michelle Obama on Tuesday (local time), the former US president recalled that Harris in her capacity as the attorney general of California had stood up for children who had been victims of sexual abuse.

"Kamala Harris is ready for the job," Obama said noting that she fought big banks and for-profit colleges, "securing billions of dollars for the people they have scammed".

Taking a swipe at Donald Trump, Obama said that the US didn't "need four more years of bluster and bumbling and chaos."

"Here's a 78-year-old billionaire who has not stopped talking about his problems since he rode down on his golden escalator nine years ago" Obama said of Trump.

"We have seen that movie before, and we all know that the sequel is usually worse," Obama said adding that "America is ready for a new chapter. America is ready for a better story. We are ready for a President Kamala Harris."

In his speech, Obama also praised Joe Biden and said that choosing the latter his as his vice president in 2008 was one of the best "big" decisions he made during his candidacy.

"Joe and I come from different backgrounds, but we became brothers, and as we worked together for eight, sometimes pretty tough years, what I came to admire most about Joe wasn't just his smarts, his experience -- it was his empathy and his decency and his hard earned resilience; his unshakable belief that everyone in this country deserves a fair shot," said Obama.

Meanwhile, Michelle Obama who captivated the crowd with her rousing speech also went tough against Donald Trump, while only rarely naming him as per a commentary in The Hill.

"Hope is making a comeback," the former first lady said early in her speech, drawing a direct line between her husband's historic 2008 presidential campaign and Harris's quest this year, the US publication noted.

In her fiery speech Michelle said that of the two major candidates in this race, "only Kamala Harris truly understands the unseen labour and unwavering commitment that has always made America great."