Nicole Gaudiano

USA TODAY

PHILADELPHIA — Sen. Bernie Sanders, in a bid to bridge the Democratic Party's divide between his backers and supporters of Hillary Clinton, moved Tuesday to give Clinton the party's presidential nomination by acclamation.

His motion at the Democratic National Convention came after the roll call of states and was greeted with chants of "Bernie! Bernie!"

As they'd signaled from the start of the convention on Monday, many Sanders delegates weren't ready for unity.

Angered by a nomination process they felt was rigged, they swarmed out of the Wells Fargo Center after Clinton's official nomination and congregated outside -- and inside -- a nearby media tent as at least two-dozen law enforcement officers stood guard.

Shyla Nelsa, a Vermont delegate who was among those nominating Sanders on stage, said the walkout was an "organized, peaceful, nonviolent action called "no voice, no unity."

"This was clearly in its context a gesture to honor our constituents back home," she said. "Many, many of our constituents all over this country feel that their voices have not been adequately heard in this process."

Among other things, Sanders' pledged delegates complained that superdelegates, the party leaders and elected officials who can vote for the candidate of their choice at the convention, had given Clinton an unfair advantage in the nominating contest. They also were infuriated by leaked Democratic National Committee emails that revealed attempts by the committee to undermine Sanders' campaign.

Amid the crush of protesters, about 10 delegates with black tape over their mouths sat in a semicircle holding hands in front of a sign lettered in black tape that said "vote fraud." Some people held signs that said "Rigged" and "#DemExit." Others made peace signs.

"It's an acknowledgement that this process didn't satisfy everyone," said Gus Madrid, a North Carolina delegate, said of the protest. "People feel disenfranchised."

Sanders, I-Vt., had waited 15 months to watch his delegates cast ballots for him at the convention, hoping against the odds that he would be the candidate accepting the nomination. During his speech to the convention on Monday, Sanders told his delegates he was looking forward to their votes, even while urging them to help Clinton defeat GOP nominee Donald Trump in November.

“I understand that many people here in this convention hall and around the country are disappointed about the final results of the nominating process,” he said. “I think it’s fair to say that no one is more disappointed than I am. But to all of our supporters – here and around the country – I hope you take enormous pride in the historical accomplishments we have achieved. Together, my friends, we have begun a political revolution to transform America and that revolution – our revolution – continues.”

What is a convention roll call vote, and what does it mean for Clinton?

On Tuesday, Vermont went last in the roll call of states. After all of Clinton's and Sanders' delegate numbers had been announced, Sanders said, "I move that Hillary Clinton be selected as the nominee of the Democratic Party." He kissed his wife Jane and waved to the cheering crowd, saying "thank you" and pressing his lips together in a stoic expression.

At the 2008 Democratic convention, Clinton interrupted the official roll call vote to move that then-Sen. Barack Obama be selected by acclamation.

Sanders told USA TODAY recently it was important for his delegates to cast their ballots for him at the convention because “I want the country and the world and our people to appreciate the kind of success we’ve had."

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'Hillary Clinton must become the next president,' Sanders tells convention

In a moving moment at the convention unfolding in the City of Brotherly Love, Sanders’ older brother, Larry, of Oxford, England, fought back tears as he announced the delegate vote tally for Democrats Abroad, a contest his brother won.

Larry Sanders said he and his brother's parents, Eli and Dorothy, “did not have easy lives and they died young” and they would be “immensely proud of their son and his accomplishments.” Bernie Sanders, shown with his wife in the family box, could be seen holding back tears.

“They loved the New Deal of Franklin Roosevelt and would be especially proud that Bernard is renewing that vision,” Larry Sanders said, his voice cracking with emotion. “It’s with enormous pride that I cast my vote for Bernie Sanders.”

In nominating Sanders ahead of the roll call, Rep. Tulsi Gabbard of Hawaii said the Vermont senator had inspired a "movement of love" that calls on Americans to care about people who have lost their jobs or are buried under college debt, and about the environment, veterans and lives lost in unnecessary wars.

"Because this is a movement fueled by love, it can never be stopped or defeated," she said.

Bernie Sanders delegates speak out

While nominating Sanders, Paul Feeney, legislative director of IBEW Local 2222, encouraged delegates to send the message that the party is united and that "our movement has just begun."

"Stay engaged, stay active, stay fired up, because we have shown this country that people-powered politics can never be defeated," he said.

Outside the Wells Fargo Center, Mark Lasser, a Colorado delegate, said Sanders had broken promises to take the fight to the floor of the convention and to avoid letting Clinton win by acclamation.

"Its a lie," he said. "You don't have to pretend that it's acclamation. Anyone can open their eyes and see that there's not unity."

Michael McCorkle, a Colorado delegate, said delegates are upset with an unfair process and party bias against them -- not with Sanders.

"He was so brave," McCorkle said. "People are disappointed that he's being forced into this concession. I don't think anyone has hard feelings about Bernie."

Follow @ngaudiano on Twitter.

Bernie Sanders urges delegates not to boo