Sen. Bernie Sanders (I-Vt.), left, and Democratic National Committee Chairman Tom Perez at a Democratic rally in April 2017 in Mesa, Ariz. (Matt York/AP)

Democrats are meeting in Providence, R.I., this weekend to advance changes to their presidential primaries, hoping to end the bitterness that followed the 2016 election — with an emphasis on “hoping.”

The push for changes, which began nearly two years ago at the Democrats’ Philadelphia convention, concerns rule revisions proposed by a Unity Reform Commission and vetted by the standing Rules and Bylaws Committee. The most high-profile battles have come over the role of superdelegates, the party leaders and members of Congress whose votes are not pledged to follow the results of any primaries.

Sen. Bernie Sanders (I-Vt.), who failed to get the 2016 Democratic presidential nomination, has campaigned to end the voting power of most superdelegates, keeping the issue alive.

“You had superdelegates voting for Hillary Clinton in states that I won pretty handsomely,” Sanders said this week in an interview with The Washington Post’s James Hohmann. “And now there is agreement among Tom Perez and our people and a lot of the Clinton people to say we should reduce the number of superdelegates.”

Perez, the Democratic National Committee chairman gave House Democrats a preview Tuesday of a potential compromise: Superdelegates would get no vote on the first ballot at the next Democratic convention. While they could endorse whomever they wanted, and while they would be able to attend the convention and vote on other matters, the 700-odd elected officials and party leaders who currently have automatic voting status would not vote on the presidential nominee unless the contest dragged to a second ballot.

That idea landed with a thud among some party leaders but mollified Democrats who have called for superdelegates to be abolished.

“The whole intent was to make sure the unelected delegates did not have a disproportionate role in deciding our nominees,” said Rep. Raúl M. Grijalva (D-Ariz.), one of a handful of congressional Democrats who endorsed Sanders. “I think that this would achieve that.”

The idea differs slightly from a compromise that emerged from the Unity Reform Commission, where supporters of Hillary Clinton’s 2016 campaign slightly outnumbered supporters of Sanders. The commission recommended removing the unpledged status of 400 delegates, binding them instead to the primary and caucus results in their states.

In 2016, for example, Sanders defeated Clinton by 15 points in West Virginia’s Democratic primary, but six of the state’s eight superdelegates backed Clinton over Sanders. Under the commission’s recommendation, Sanders would have won 18 of the state’s 29 pledged delegates and five of the eight superdelegates.

The proposal floated this week — which has been described but not put down in print — goes further than that, in ways that carry potential negative repercussions if the next Democratic primary is divided among multiple strong candidates. In 2016, Clinton won a clear majority of pledged delegates and would have secured the nomination on the first ballot even if no superdelegates had been permitted to vote.

But had the new proposal been in place in 2008, the pledged delegate majority would have come down to the controversial decision to give half-delegate votes to Michigan and Florida, after those states flouted party rules and scheduled early primaries. In a three-way primary in which no candidate had a majority on the first ballot, superdelegates would determine the nomination on the floor in subsequent ballots — something the past 50 years of party actions had been designed to prevent.

But every idea for curtailing superdelegate power has been angrily opposed by a rump of Democratic Party leaders. Bob Mulholland, a pugnacious former California party strategist and current DNC member, included reporters on an email he sent to the chairs of the Rules and Bylaws Committee and addressed to Perez and Rep. Keith Ellison (D-Minn.), the DNC’s vice chair.

“The two of you are conspiring with Bernie Sanders to block Congress members John Lewis, Maxine Waters, Barbara Lee and the rest of the congressional delegation, Governors, State Party Chairs and the rest of us DNC Members from entering our Convention floor in 2020 as voters,” Mulholland wrote. “I don’t know if you will have paid thugs at the doorways to beat up Congressman Lewis and the rest of us or not.”

To emphasize his point, Mulholland attached a photo of police beating Lewis at the 1965 march for voting rights in Selma, Ala.

No final decision on DNC rules will be made in Providence. The party committee has until June 30 to affirm or reject the amended Unity Reform Commission changes, and the deal that set up the commission would allow votes to restore more of its recommendations at the next full DNC meeting, in August.