Presidential candidate Bernie Sanders prepares to speak for a video to supporters at Polaris Mediaworks on June 16 in Burlington, Vt. (Matt McClain/The Washington Post via AP)

Over the weekend, as Democratic presidential candidate Bernie Sanders made no public appearances, his supporters won their latest victory. Nebraska Democrats were meeting to elect convention delegates and new state party leaders. Chuck Hassebrook, the party's 2014 nominee for governor, was competing for the chairmanship with Jane Fleming Kleeb, a leading activist against the Keystone XL oil pipeline. Hassebrook had backed Hillary Clinton for president; Fleming Kleeb had supported Sanders.

Fleming Kleeb won, and it wasn't close. Meanwhile, Nebraska Democrats agreed to recommend that superdelegates, instead of enjoying free agency, be bound in future elections to the winners of state contests. They joined Alaska, CaliforniaHawaii, IowaMaine and Minnesota in a growing roll call of states that want superdelegates abolished or hemmed in -- another priority of the Sanders campaign.

In his public statements, Sanders has laid out a three-pronged Democratic Party reform plan. Superdelegates should be abolished, primaries should be open to all voters and "the most progressive platform" in party history should be approved in Philadelphia.

Progress has been made on all three fronts. Sanders's allies on the drafting platform committee have struggled to get the party to endorse new language on Israel's relationship with the Palestinians. But in conversations with Clinton delegates, there have been reasons for optimism on the rest of the Sanders policy planks -- Medicare for all, for example -- and on the reform of superdelegates.

The trickiest reform idea is on how primaries should be conducted. It is up to each state party whether it holds a caucus or a primary. Clinton allies, who think the primaries might have ended much sooner had Sanders not thrived in lower-turnout caucuses, succeeded in getting California's Democratic Convention to call for an end to caucuses alongside an end to superdelegates. It's not up to the parties, necessarily, if states allow independents to vote in their primaries, or allow same-day registration.

"The Democratic Party does have input and leverage to make this happen," said Mark Longabaugh, a Sanders strategist working on the primary reform push. "Rather than the stick of sanctions, the party could incentivize states with more or bonus delegates. The party did this in response to front loading in the 2008 primaries. In 2008, 70 percent of delegates were chosen before March 1. In 2016, only 4 percent of the delegates were chosen before March 1. The party awarded more delegates to states who scheduled primaries and caucuses later on the calendar."

Sanders, who would be 79 in November 2020, is not the most likely beneficiary of the changes. Historically, party leaders who've pushed to open primaries have wanted to attract more moderate voters. But in the 2008 and 2016 contests, open primaries helped the candidates considered the most progressive -- Barack Obama and Sanders. Close to 50 percent of voters younger than 30 have not signed up with either party, making them the leading edge of a trend in which some harder, ideological voters have remained independent.

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