Chicago (CNN) Democrats on Saturday voted to chip away at the role party insiders play in choosing the party's presidential nominee in one of the biggest changes to the process in decades.

The move to limit the influence of "superdelegates" at the party's convention ahead of the 2020 presidential primaries ended an emotional and tumultuous two-year effort born out of the divisive 2016 contest between Vermont Sen. Bernie Sanders and former Secretary of State Hillary Clinton, who went on to become the Democratic nominee.

In a surprisingly united vote, almost all members of the Democratic National Convention curtailed the ability of the superdelegates to vote on the first ballot for the party's presidential nominee beginning with the next election. The group of about 700 automatic, unpledged party leaders, elected officials and activists previously were able to back whichever candidate for the nomination they chose.

The move ended a vehemently contested debate that had pitted a majority of DNC members supporting the change against two former party chairs, members of the Congressional Black Caucus, and others who opposed the new rules. Both sides came together to pass the overhauled process ahead of the next presidential campaign.

Saturday's vote officially barred the superdelegates from voting on the first ballot to choose the party's presidential nominee unless a candidate has secured a majority of the convention using only pledged delegates, whose votes are earned during the primary process.

Beginning with the 2020 nomination process, candidates will no longer be able to count superdelegates if they want to win the party's nomination on the first ballot of voting at the convention. This makes it impossible for superdelegates to change the outcome of the pledged delegates' will, which has never occurred since superdelegates were created ahead of the 1984 campaign.

"Today is a historic day for our party," said DNC Chair Tom Perez. "We passed major reforms that will not only put our next presidential nominee in the strongest position possible, but will help us elect Democrats up and down the ballot, across the country. These reforms will help grow our party, unite Democrats, and restore voters' trust by making our 2020 nominating process the most inclusive and transparent in our history."

The change stems from a tumultuous 2016 primary campaign, in which Sanders' supporters accused the superdelegates of having too much influence over the outcome. The overwhelming majority of them supported Clinton.

The bitter divide within the party over the changes came to an unexpected close when former DNC Chairman Don Fowler, who was adamantly against the changes and led the opposition, moved to vote by acclimation instead of a ballot vote.

"You always want unity. I still am much opposed to most of what's in that document, but more people than I wanted it," Fowler told CNN after the vote. "You've got the elections to take care of in two and half months, then the convention and all the 2020 cycle starts. That's just a whole different ballgame."

The battle for superdelegates

Perez and DNC officials were pleasantly surprised by the change from Fowler and other members who were against the reform, but members of the DNC Black Caucus were split on the reforms, with those opposed in agreement with Fowler that the move was a form of voter disenfranchisement.

"The right to vote is sacred," said former DNC Chair Donna Brazile, who was against the changes, ahead of the vote. "It's an insult to democracy."

Other Black Caucus members like Michael Blake --who worked for President Barack Obama in the White House on African American outreach and engagement, refuted those charges.

"This is not disenfranchisement at all. The person that has their vote taken away and has been purged -- that's the person we need to be fighting for," he said Friday before the vote. "Voters want us to be listening to them, and this is a way to show that we are listening -- to show that we are understanding the changes that had to be made after 2016."

Democrats created a Unity Reform Commission at the last convention to study and recommend changes to the delegate process and other party reforms. Those recommendations were submitted to DNC committees for consideration and were amended for a full party vote at their meeting in Chicago.

Changes within party for more transparency, inclusion

DECLARING YOURSELF DEMOCRAT: Candidates seeking the party's presidential nomination will now have to declare themselves as Democrats in writing to the DNC, a change pointed at Sanders, who is technically an Independent senator that caucuses with the Democrats.

CAUCUS OVERHAULS: Caucuses have also undergone some changes as well. The party is officially encouraging states to use government-run primaries, give access to people who can't make the actual caucus (like shift workers, those with disabilities and language difficulties), implement same-day party change and voter registration, report statewide presidential preference on the first vote, and ensure that all national delegates represent the same original vote for the first caucus vote.

TRANSPARENCY: The DNC is now required to be more transparent on operations, finances, and dealings with Democratic presidential candidates, such as in providing information on fundraising, and vendor agreements. Information about these things should be made available to all Democratic candidates, the language says.

GENDER INCLUSION: Language for rules that mandate gender equality in committees, caucuses and other bodies has also been expanded to include members who are gender nonbinary . DNC committees and caucuses have included gender equality in the past, meaning they had to declare themselves male or female. Gender nonbinary members will no longer have to declare themselves as either. Instead, going forward the requirement now says the divide between those who identify as men and women have a variance of one.

How to win the Democratic nomination for president

Democrats who want to win the party's nomination in 2020 will now only be able to do that with pledged delegates if they want to avoid a floor fight at their convention.

Using simplified numbers (these do not reflect the actual number of delegates that will be voting at the 2020 convention), here's how it will work among the 1,200 total convention delegates (1,000 pledged and 200 unpledged):

SCENARIO ONE: A candidate earns a majority of pledged delegates only (501 to 600 pledged delegates).

OUTCOME: Only pledged delegates vote on the first ballot for president. The candidate with a majority of pledged delegates would then become the party's nominee.

SCENARIO TWO: A candidate earns a majority of the convention in pledged delegates (601 to 1,000 pledged delegates).

OUTCOME: Pledged and superdelegates can vote on the first ballot for president. The candidate with the majority wins the Party's nomination.

(In scenarios one and two, the nominee would be the same person; the only difference would be who would vote on the first ballot).

SCENARIO THREE: No candidate earns a majority of either pledged or all delegates in the primary contests, most likely due to multiple candidates having run during the 2020 process (1 to 500 pledged delegates).

OUTCOME: Only pledged delegates would vote on the first ballot, but with no majority winner, the party would then vote on a second ballot (and more if needed). Superdelegates would vote beginning with the second ballot.

Pledged delegates could still change their votes to avoid a second ballot if their candidate drops out and "releases" them, in which case they could vote for their personal preference. All delegates become unpledged after the first vote. The last Democratic convention to go beyond the first ballot was in 1952.

What stays the same for superdelegates

Superdelegates, like all other delegates, have other responsibilities at the convention, which are staying the same.

They are free to campaign and endorse the candidate of their choice at any time during the primary process. This has been a source of contention for some Democrats, who created rules to limit their ability to publicly endorse or campaign for presidential candidates. Those proposals failed in committee.

At the convention, they will still have complete floor access and be part of the hotel process to get their room assignments for the week. They remain eligible to serve on the rules, platform and credential committees. These are critical to the convention and the party.

On the floor, they can vote for a vice presidential nominee on all ballots however they choose.

Moving forward

DNC members came into the meeting wanting to chart their path forward for 2018 and 2020, despite the significant differences they had over the delegate changes.

Though some African American members still opposed the vote and had it recorded, the overwhelming majority of members on both sides came together to show their determination to win back Congress and the White House -- one of the biggest topics of discussion in their private conversations and meetings.

"I was skeptical of the proposal, but I'm a team player, and the most important thing we can do is elect Democrats this fall and in 2020," said DNC member Bill Owen, who supported Fowler's move. He went on to paraphrase another Democratic leader.

"John Kennedy said, 'Let us go forth from here to lead the land we love, asking his blessing but knowing God's work out here is truly our own," Owen said.