Joe Biden has officially been anointed the Democratic presidential candidate at the party's convention, helped over the line with some glowing testimonials from elder statesmen.

Two Democratic former US presidents, Bill Clinton and Jimmy Carter, and former Secretary of State Colin Powell, a Republican, endorsed Mr Biden.

Mr Clinton said President Donald Trump had brought "chaos" to the Oval Office.

Mr Trump trails Mr Biden in opinion polls ahead of November's election.

This is Mr Biden's third White House bid - his coronation as the Democratic nominee represents a remarkable turnaround given that his campaign appeared to be in danger of collapse in February.

On the second night of the party convention on Tuesday, with the theme "leadership matters," Mr Clinton delivered the key address.

"Donald Trump says we're leading the world," Mr Clinton said in his five-minute message pre-recorded from his home in Chappaqua, New York. "Well, we are the only major industrial economy to have its unemployment rate triple.

"At a time like this, the Oval Office should be a command centre. Instead, it's a storm centre. There's only chaos."

Following addresses from former First Lady Michelle Obama and Senator Bernie Sanders on Monday, Tuesday's speeches aimed to show voters how the Democratic party is the best suited to repair problems at home and abroad.

Mr Powell said Mr Biden shares "the values I learned growing up in the South Bronx and serving in uniform".

The decorated four-star general said he supports him for president because "we need to restore those values to the White House".

In June, Mr Powell - who served under President George W Bush - called President Trump a liar and endorsed Mr Biden.

Cindy McCain, the widow of Republican Senator John McCain, also spoke about the friendship between her late husband and Mr Biden.

They join several Republicans who have endorsed Mr Biden, including former Ohio Governor John Kasich during the first night of the convention. (BBC)

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