After 2016, Democrats could be on track for much less infighting at 2020 DNC convention

Four years after raucous and contentious scenes, with Sen. Bernie Sanders' delegates on occasion openly booing from the party’s convention floor, Democrats this year are positioned for much less drama and set to show off a far more united front.

"While Joe Biden and I, and our supporters, have strong disagreements about some of the most important issues facing our country, we also understand that we must come together in order to defeat Donald Trump, the most dangerous president in modern American history," Sanders said in early July.

Though some of his delegates have made noise about opposing the platform, Sanders voted for the current party platform and, more, distanced himself from other progressives publicly opposing the current charter in recent interviews.

He even attempted to assuage concerns about his liberal base's priorities come November on the eve of the convention's opening night.

"The overwhelming majority of progressives understand that it is absolutely imperative that Donald Trump be defeated," Sanders told ABC's "This Week" on Sunday. "There may be disagreements. A lot of my supporters are not enthusiastic about Joe Biden. You know why? I ran against Joe Biden."

The theme of this year's convention is "Uniting America" -- a more concerted effort to reconcile ideologically divergent factions in the party.

Last time around, Sanders' delegates used their leverage -- and the threat of a floor flight -- in the process for crafting the party's platform. They pushed the non-binding blueprint of the party's goals and vision to embrace some of their progressive ideals, such as, a $15 minimum wage, closing private prisons among other criminal justice reforms, and concessions on climate change, including support for limits to fracking.

Days before the convention, Wikileaks released thousands of internal emails from the DNC, which showed some top party officials appearing to aid Clinton's campaign during the primaries, including disparaging emails from Rep. Debbie Wasserman Schultz, then the chairwoman of the DNC, about the Sanders campaign.

Sanders allies, both frustrated by the outcome of the race and enraged over the leaked emails, arrived at the Philadelphia convention loaded for bear -- turning a typically dull affair into a tense and bitter clash with open fissures on full display.

In an attempt to stop the bleeding, the party committed to set up the Unity Reform Commission, which consisted of representatives from both the Sanders and Clinton camps, to examine and propose structural changes to the nominating process after the convention.

The commission, which ultimately approved of stripping superdelegates of much of their power, paved the way for a less contentious primary process in 2020.

"It's night and day," Larry Cohen, a longtime ally of Sanders who is also chair of Our Revolution, a nonprofit political organization aligned with Sanders, said of the primary season in July. "The differences in those four years, huge. You don't hear any of those candidates -- we've had more candidates than ever -- saying that it was rigged. It wasn't."

For any convention, party rules allow for delegates on the three standing committees who muster enough support to force proposals, known as minority reports, to be brought to the convention floor for a vote. But the reports can cause headaches if they appear to expose of divisions within the party's ranks.

This year, no minority reports were submitted, a Democratic official told ABC News. Although a small procedural tool, the lack of any possible debates over policy or rules reinforces Democrats' efforts to put unity out front at the convention.

Earlier this year, seeking to head off the divisiveness that defined the 2016 race, Biden and his team began an outreach campaign before Sanders officially endorsed him that included a mild embrace of some more progressive policies like lowering the Medicare eligibility age to 60 and expanding his support for various student debt forgiveness policies.

Unlike 2016, Sanders quickly stood behind Biden once it became clear that the former vice president would become the nominee -- endorsing him a week after his departure from the race. Sanders' exit from the Democratic primary set off the start of negotiations between the two campaigns.

"Bernie gets a lot of credit for his passionate advocacy for the issues he cares about. But he doesn’t get enough credit for being a voice that forces us all to take a hard look in the mirror and ask if we’ve done enough," Biden wrote in a Medium post after Sanders dropped out.

The early olive branch by the Biden campaign was followed by the creation of the "unity task forces," formed by both the Biden and Sanders campaigns to deliver a unified set of policy recommendations on issues -- ranging from health care to the economy to criminal justice reform -- to the Democratic National Convention's Platform Committee. The task forces reflected the breadth of the party -- including members of the old guard, such as former secretary of state John Kerry, and young, progressive stars, such as, Rep. Alexandria Ocasio-Cortez, D-N.Y.

Sanders has repeatedly returned to and praised the work done during the joint Sanders-Biden "unity task force" meetings and argued the new party platform included many recommendations and concessions to the progressive wing of the party. The 2020 platform includes a nod to Medicare for All, saying that the party "welcomes advocates who want to build on and strengthen the Affordable Care Act and those who support a Medicare for All approach."

According to a senior campaign aide, Sanders has felt content and included working with the former vice presidential since the primaries wrapped.

This aide remarked too that, for Sanders' staff, working with team Biden has felt noticeably more open and collegial compared to working with the Clinton teams four years ago, and that Sanders is telling his supporters to gear up for pushing Biden after they help him get elected first.

Recent down-ballot wins, from up-and-comers like Cori Bush and Jamaal Bowman, have left many progressive grassroots organizers upbeat and confident.

The move by Biden was seen by some establishment Democrats as a key factor in bridging a divide that marred the 2016 race as Democrats openly showed their struggle to unify behind the Democratic nominee in the first matchup against Trump.

"It was the right thing substantively to engage Bernie Sanders after the election," former President Barack Obama said on his former campaign manager David Plouffe's podcast "Campaign HQ" last week. "A lot of the so-called divisions within the Democratic Party, I think are not going to be a major factor in the election."

But still some Democrats in the party's liberal wing feel the party's policy platform does not go far enough, particularly on the issue of health care.

Several hundred Sanders delegates are expected to vote oppose the platform over Medicare for All, Politico reported. Two high-profile Sanders allies, Reps. Ro Khanna, D-Calif., and Rashida Tlaib, D-Mich., also publicly announced they would vote against the party's platform for falling short on health care.

"When we say that healthcare is a human right, we must truly mean it—and fight for it," Khanna, who was a national co-chair of Sen. Bernie Sanders's presidential campaign, wrote in an op-ed.

Despite the dissenters, the convention's virtual format might make it harder for any boos and jeers during the choreographed four-night gathering, although there still could be some disputes bubbling to the surface remotely.

For Sanders, who is set to take the stage on Monday night, the intraparty fights are over, as he believes the party has moved further to the left. But he said, there is always room for progress to be made.

"The progressive movement has been making enormous progress," Sanders said on Sunday, "in bringing the American people in our direction, especially the younger generation...We are going to continue the fight for Medicare-for-all."

ABC News' Adam Kelsey contributed to this report.