For a party that endured a wide-open presidential primary with more than two-dozen candidates ranging from the left to the middle – and with the wounds of disunity from 2016 still healing – achieving party unity at this week’s Democratic National Convention is a top priority.

And Democrats are intent on making sure history doesn’t repeat itself.

WHO'S SPEAKING AND WHEN AT THE DEMOCRATIC CONVENTION

Four years ago after a divisive primary battle, populist champion Sen. Bernie Sanders of Vermont endorsed presumptive nominee Hillary Clinton. But there was plenty of bad blood at that summer’s Democratic convention. The confab, held in hot and humid Philadelphia, was rocked by progressive protests that were televised live on the national cable news networks. The deep divisions were a contributing factor in Donald Trump’s upset victory over Clinton.

Fast forward four years and once again the left fell short, as progressive standard-bearers Sanders and Sen. Elizabeth Warren of Massachusetts were defeated in the primaries by more moderate former Vice President Joe Biden.

But this time around, with a common enemy in the White House, the worst pandemic this country’s faced in a century and a primary process that ended much earlier than four years ago, a repeat performance of the widescale enmity of 2016 could well be avoidable.

In this 2016 file photo, Bernie Sanders supporters are seen protesting outside the Democrats' convention in Philadelphia. (FNC)

In this 2016 file photo, Bernie Sanders supporters are seen protesting outside the Democrats' convention in Philadelphia. (FNC)

That’s not to say voices on the far left aren’t angry, however, and the virtual convention represents a key test of whether Sanders adherents can be kept in the fold. Plenty of them have vocalized their displeasure toward Biden as the nominee – and with the former vice president’s naming last week of Sen. Kamala Harris of California as his running mate.

There was an outcry by some on the left in recent days at the inclusion of moderate Democrat and former New York City Mayor Mike Bloomberg, who was a 2020 primary contender, and former Ohio governor and 2016 GOP presidential candidate John Kasich as convention speakers -- while some well-known progressive voices didn't make the list. And some Sanders delegates are vowing to vote against a party platform that doesn't include "Medicare-for-all."

PROGRESSIVES BLAST DEMOCRATIC OFFICIALS OVER CONVENTION SPEAKERS LINEUP

“There are people that are really disappointed in how the primary came out and there are certainly going to be a number of restive elements among Bernie Sanders delegates,” Neil Sroka, communications director for the progressive group Democracy for America, acknowledged.

But Sanders has been given a speaking slot for the convention's opening night on Monday, meaning he'll help set the tone for the entire week. And both Sanders and Warren – as well as other major progressive leaders and organizations – are firmly backing Biden and Harris.

Even before he clinched the nomination, Biden started adopting some of Sanders and Warren’s leading progressive policy proposals. And Biden and Sanders teamed up to form task forces that found common ground on key issues. Rep. Alexandria Ocasio-Cortez of New York – a leader of the younger generation of progressives and champion of the Green New Deal – co-chaired the climate change panel.

“The Biden campaign – partly because Biden personally had a close relationship with Sen. Sanders – has done a better job of reaching out to the grassroots base,” said Sroka, a locally elected official in Michigan and 2020 convention delegate who supported Sanders in this year’s nomination race. “They’ve done a better job not throwing their victory in the faces of progressives – I think because they saw how unhelpful that was in 2016.”

Sroka noted that another “difference between 2016 and 2020 is that it wasn’t exactly clear in 2016 that the progressive movement would be the ascendant force in the Democratic Party going forward.”

He said that now “it’s very clear that the future of the Democratic Party is continuing to move in a progressive direction” and added that “Biden has underscored this by calling himself a ‘transitional’ president – that gives progressives much more room to feel like they have a stake in this party.”

TRUMP TO CAMPAIGN IN SWING STATES DURING DEMOCRATIC CONVENTION

Veteran Democratic consultant and communications strategist Lynda Tran said that a core goal at the convention is “projecting a level of unity across the party at large from the more progressive side of things to the more moderate wing of the party to show that everybody’s in lockstep and everybody’s united.”

Adam Green, co-founder of the Progressive Change Campaign Committee which backed Warren in the primaries, emphasized that "progressives are inherently energized to vote against Trump.”

His suggested that “if Biden wants to energize progressives to donate and volunteer to get every last person to vote, he will use the convention to shine the spotlight on progressive issues he's embraced like canceling student debt and expanding Social Security benefits during this pandemic, more corporate accountability, and taxing the rich to pay for things like clean energy jobs."

There was plenty of discord heading into the Democratic convention four years ago – but fires were further fueled after a collection of compromising Democratic National Committee emails stolen by hackers who were alleged to be Russian intelligence agency operatives were released by Wikileaks on the eve of the confab.

Sroka noted that the challenges Clinton faced heading into the convention were “inflamed by the Wikileaks releases. That was a huge conflagrating factor.”

Another major difference – this year’s convention will be virtual, due to serious concerns of large gatherings of people amid the coronavirus pandemic.

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Without a packed arena full of delegates and grassroots activists, discord will be harder to achieve. “You kind of need a wildfire to emerge and that can’t really happen when people are as distanced as they are,” Sroka said.