Nicole Gaudiano

USA TODAY

WASHINGTON — Sen. Bernie Sanders called Tuesday for a “fundamental transformation” of the Democratic Party that would include new leadership at the Democratic National Committee, electoral reform and a progressive agenda that makes it "crystal clear" Democrats stand with working people and the poor.

The Vermont senator, speaking outside his Washington campaign headquarters, said his presidential campaign has been about “transforming America” and he plans to take that fight to the Democratic National Convention in Philadelphia in July.

Sanders also called for open primaries -- in which independents could vote for Democratic candidates -- and for doing away with superdelegates, the party officials and leaders who are free to vote for the candidate of their choice at the convention. And he argued for same-day voter registration.

"We need a party which is prepared to stand up for the disappearing middle class, for the 47 million people in this country who are living in poverty, and take on the greed of the powerful special interests that are doing so much harm to this country, who have so much power over the political and economic life of our country," he said.

Sanders still has not conceded the nomination race, even though presumptive Democratic presidential nominee Hillary Clinton has claimed victory after securing the required 2,383 delegates.

Clinton and Sanders met late Tuesday at the Capital Hilton in Washington for about 90 minutes, as they had agreed to do after the California primary. A Clinton campaign official said the two discussed unifying the party while Sanders’ spokesman Michael Briggs said they talked about how best to bring more people into the political process. They otherwise gave similar descriptions of the meeting, saying it was a positive discussion that focused on “the dangerous threat” Donald Trump poses. Both camps said they discussed raising the minimum wage, campaign finance reform and affordable college, while Briggs included universal health care. They also said they agreed to continue working on developing the Democratic Party platform.

Sanders' comments earlier in the day about transforming the Democratic Party came as Washington held the final nominating contest of the Democratic presidential campaign season. Clinton won the city's primary with 78.7% of the vote. Twenty delegates were at stake in the contest.

Sanders' call for electoral reform and new DNC leadership recalled two prominent sore points from his campaign.

He feuded often with the DNC and its chairwoman, Rep. Debbie Wasserman Schultz of Florida, over the Democratic debate schedule, access to a DNC voter database, a joint fundraising agreement between the DNC and Clinton, and representation on convention committees. Sanders, who has raised money for Wasserman Schultz's primary opponent, said the party needs a new leader who works vigorously to bring people into the political process.

“I know political parties need money, but it is more important that we have energy, that we have young people, that we have working class people who are going to participate in the political process and fight for their kids and for their parents,” he said Tuesday.

Wasserman Schultz, responding to Sanders’ comments on Meet the Press Daily, said she will focus -- through the election and up to end of her term as DNC chairwoman -- on ensuring a Democrat is elected president and the party's down-ballot candidate's also win their races.

“Democrats will come together, as we should, to make sure that we can defeat Donald Trump and elect our party’s nominee," she said. "We're all going to be one team after this primary is over."

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Sanders also has long complained about the role of superdelegates, who he says subvert the electoral process. Clinton consistently led him by a huge margin in those delegates.

“We need to also make sure that superdelegates do not live in a world of their own but reflect, reflect, the views of the people in their own states,” he said.

Sanders hasn’t spoken of winning the nomination since losing California's primary on June 7. Instead, he has focused his message on ensuring that presumptive GOP nominee Donald Trump doesn’t win the presidency. But he has so far resisted pressure from Democrats to concede and endorse Clinton. Clinton also won endorsements last week from President Obama, Vice President Biden and Sen. Elizabeth Warren of Massachusetts, a hero of the progressive movement that Sanders represents.

Briggs said Sanders will speak via live video "directly to grassroots supporters from Burlington (Vt.) on Thursday night about how the revolution continues."

"I expect that he will be a candidate through the Democratic National Convention in Philadelphia, as he has said before," Briggs said.

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Also Tuesday, Sanders met behind closed doors with Senate Democratic colleagues, who gave him a warm reception, according to those who attended.

Sen. Claire McCaskill, D-Mo., an early backer of Clinton's who served as an anti-Sanders surrogate in the primary, said she’s not concerned about Sanders' plans to take his campaign to the convention.

"He was very clear that he thought there were things that we had to focus on and do better and I don’t think it was met with any disagreement in the room," she said. She also said the Democratic senators Sanders spoke to Tuesday acknowledge that he commands enthusiastic support from a large number of voters, "many of whom had not traditionally participated.”

Sen. Tom Carper of Delaware said Sanders told colleagues he plans to play an active role in crafting the party's platform.

“He mentioned he has every intention of being involved in the platform process and making sure his 2,000 delegates have the opportunity to have their voices heard,” at the party's convention, Carper said.

Senate Minority Leader Harry Reid of Nevada called the meeting with Sanders "terrific."

"Sen Sanders took time to talk to us about his experiences. It was really very, very moving,“ Reid said.

Sanders won 22 states and 45% of pledged delegates during his quest for the nomination, and he consistently led Clinton overwhelmingly among 18-29-year-olds. His calls for a "political revolution" and for a fight against a "rigged economy" and "corrupt" campaign finance system drew nearly 1.5 million people to his rallies and a record 8.2 million individual contributions from about 2.5 million donors. He raised about $228 million, largely through fundraising emails to supporters.

At a rally in Washington on Thursday night, supporters interrupted the beginning of his speech with chants of “Thank you, Bernie,” and some called for him to stay in the race.

“I think (Clinton) thinks we can only make small changes,” said Maggie Murphy, 26, a Washington resident who works at a non-profit. “We do need a revolution. We need to stop accepting Republicans making us meet them in the middle. We need to stand to the left.”

Contributing: Donovan Slack and Deirdre Shesgreen, USA TODAY