Bernie Sanders urges his supporters to vote for Joe Biden over Donald Trump

Four years ago, Bernie Sanders’ supporters refused to fall in line behind Hillary Clinton. He clearly doesn’t want that to happen again.

Bernie Sanders has urged his supporters to fall in line behind the Democratic Party’s presidential nominee, Joe Biden, in a united effort to defeat Donald Trump.

Mr Sanders was the runner up in the Democratic primaries earlier this year, just as he was in 2016, when former secretary of state Hillary Clinton claimed the party’s nomination.

The left-wing Vermont Senator was criticised in some quarters four years ago for doing too little to convince his fans to vote for Ms Clinton.

According to a post-election study, 12 per cent of Mr Sanders’ primary voters ended up casting ballots for Mr Trump.

That was a high enough number to be a decisive factor in the three key states that made Mr Trump President – Michigan, Wisconsin and Pennsylvania.

In other words, theoretically, Ms Clinton would have won the election if Mr Sanders’ supporters had voted for her instead – or even if they had stayed home, refraining from voting at all.

Speaking on the first day of the Democratic National Convention, where Mr Biden will be formally named the party’s nominee later this week, Mr Sanders made it clear he did not want a repeat of that scenario.

“We have a President who is not only incapable of addressing these crises, but is leading us down the path of authoritarianism,” he said.

“This election is the most important in the modern history of our country. In response to the unprecedented crises we face, we need an unprecedented response. A movement like never before, of people who are prepared to stand up and fight for democracy and decency.

“We need Joe Biden as our next president.”

RELATED: Michelle Obama’s ‘ice cold’ slapdown of Trump

RELATED: Virus victim’s furious daughter addresses convention

Bernie Sanders at the Democratic National Convention.

After that introduction, Mr Sanders pivoted to speak directly to the people who supported him against Mr Biden in the primaries.

“My friends, thank you for your trust, your support, and the love you showed Jane (his wife), me and my family,” Mr Sanders said.

“Together, we have moved this country in a bold new direction, showing that all of us – black and white, Latino, Native American, Asian-American, gay and straight, immigrant – yearn for a nation based on the principles of justice, love and compassion.

“Our campaign ended several months ago, but our movement continues, and is getting stronger every day. Many of the ideas we fought for, that just a few years ago were considered ‘radical’, are now mainstream.

“But let us be clear. If Donald Trump is re-elected, all the progress we have made will be in jeopardy. At its most basic, this election is about preserving our democracy.

“During this President’s term, the unthinkable has become normal. He has tried to prevent people from voting, undermined the US Postal Service, deployed the military and federal agents against peaceful protesters, threatened to delay the election, and suggested that he will not leave office if he loses. This is not normal, and we must never treat it like it is.

“Under this administration, authoritarianism has taken root in our country. I, and my family, and many of yours, know the insidious way authoritarianism destroys democracy, decency and humanity. And as long as I am here, I will work with progressives, with moderates, and yes, with conservatives, to preserve this nation from a threat that so many of our heroes fought and died to defeat.

“Joe Biden will end the hate and division Trump has created.

“My friends, I say to you, to everyone who supported other candidates in the primary, and to those who may have voted for Donald Trump in the last election – the future of our democracy is at stake. The future of our economy is at stake. The future of our planet is at stake. We must come together, defeat Donald Trump, and elect Joe Biden.

“The price of failure is just too great to imagine.”