Nicole Gaudiano

USA TODAY

PHILADELPHIA — Sen. Bernie Sanders, working to rally his supporters behind former rival Hillary Clinton, on Monday addressed head-on their disappointment with his second-place finish in the Democratic presidential primaries.

“I understand that many people here in this convention hall and around the country are disappointed about the final results of the nominating process,” the Vermont senator said in remarks at the Democratic National Convention. “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.”

Sanders, who was greeted by his campaign signs and chants of "Bernie," said this election is about which candidate understands "the real problems facing this country and has offered real solutions – not just bombast, fear-mongering, name-calling and divisiveness." He said the country needs leadership to improve the lives of working families, children, the elderly, the sick and poor and that brings people together.

“By these measures, any objective observer will conclude that – based on her ideas and her leadership – Hillary Clinton must become the next president of the United States,” he said.

GOP nominee Donald Trump doesn’t support raising the federal minimum wage and believes in “huge” tax breaks for billionaires, he said.

“The choice is not even close,” he said.

Sanders drew cheers when he said he looks forward to his delegates' votes during the roll call Tuesday night. His references to Clinton were met with loud cheers and some boos.

Earlier, the Vermont senator urged his delegates in an email not to engage in “any kind of protest or demonstration on the convention floor” as “a personal courtesy to me” after he drew boos at a meeting with those delegates earlier Monday by saying, “We have got to elect Hillary Clinton.”

Sanders's supporters also engaged in rowdy behavior on the convention floor. Starting with Monday's opening prayer, they intermittently chanted “Bernie,” despite pleas from speakers to stop.

A few dissidents, taking a page from the GOP convention playbook, even chanted "Lock her up," referring to Clinton.

In his email, Sanders acknowledged his delegates' frustration in response to leaked Democratic National Committee (DNC) emails that show committee officials worked to undermine his campaign when he and Clinton were competing for the Democratic nomination.

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But he called it a “very positive sign” that DNC Chairwoman Debbie Wasserman Schultz announced she will resign over the email scandal.

“Our credibility as a movement will be damaged by booing, turning of backs, walking out or other similar displays,” Sanders wrote. “That's what the corporate media wants. That's what (GOP nominee) Donald Trump wants. But that's not what will expand the progressive movement in this country.”

Clinton campaign chairman John Podesta reached out to Sanders supporters in a brief speech from the podium, lauding the Vermont senator and stressing that Trump is the enemy of every Democratic delegate inside Philadelphia's Wells Fargo Center.

Comedian Sarah Silverman, a Sanders supporter, was more direct.

"To the 'Bernie or Bust' people, you’re being ridiculous," she said, drawing huge cheers from those with "Stronger Together" signs and setting off chants of "Bernie, Bernie" from others. Silverman said a "vital part" of Sanders' movement is ensuring Clinton will be president.

"I will vote for Hillary with gusto as I continue to be inspired and moved to action by the ideals set forward by Bernie, who will never stop fighting for us," she said.

The DNC on Monday issued a “deep and sincere apology” to Sanders, his supporters and the party for the “inexcusable remarks” made over email.

Unlike Sen. Ted Cruz of Texas, who shocked the GOP convention last week by not endorsing Trump during his speech, Sanders endorsed Clinton at a New Hampshire rally on July 12 and said he will do everything he can to help her defeat Trump.

Monday's outbursts on the floor, which seemed to subside after the first hour or so, followed angry anti-Clinton protests by Sanders supporters in the streets around the convention.

Democrats had hoped to project an image of unity at the convention, but the emails make that more difficult. So does Clinton's appointment of Wasserman Schultz as honorary chairwoman of her campaign's 50-state program to elect Democrats.

"It kind of all reaffirms in the minds of Bernie delegates that we were given a raw deal, that we are dealing with a rigged system, that the primary was very much rigged from the very beginning in favor of Mrs. Clinton," said Karen Bernal, a leader of California's Sanders delegation, during a morning news conference.

In his speech, Sanders cast Clinton as superior to Trump on every major issue, from economics and health care to education and the environment.

He said Clinton understands the need to raise the minimum wage and to transform energy policy, while Trump denies climate change is real. Sanders highlighted agreements he reached with Clinton on supporting expanded access to health care and free public college tuition for students from families with annual incomes up to $125,000 a year.

“And what is Donald Trump’s position on health care? No surprise there,” he said. “Same old, same old Republican contempt for working families. He wants to abolish the Affordable Care Act, throw 20 million people off of the health insurance they currently have and cut Medicaid for lower-income Americans.”

Sanders said “it’s no secret” that he and Clinton disagree on many issues, but he said they came together to produce the most progressive platform in the history of the Democratic Party.

“Our job now is to see that platform implemented by a Democratic Senate, a Democratic House and a Hillary Clinton presidency – and I am going to do everything I can to make that happen,” he said.

Most Sanders delegates surveyed in a straw poll said they want to protest the nominations of both Clinton and her vice presidential pick, Sen. Tim Kaine of Virginia, on the floor, said Norman Solomon, a Sanders delegate from California and national coordinator of the independent "Bernie Delegates Network."

"If Hillary Clinton wants to move today towards more party unity, she certainly has it within her power to say it’s a mistake to make an honorary chair out of Debbie Wasserman Schultz," Solomon said Monday morning. "We shouldn’t be honoring someone who ran such a, we now know, disreputable shop at the DNC."

Michael Tafe of Hingham, Mass., said after Sanders’ meeting with delegates that he and other Sanders delegates continue to believe the Vermont senator is the best candidate to defeat Trump and expressed unhappiness with Clinton's decision to choose Kaine as her running mate.

“We feel alienated by the Clinton campaign,” he said. “They’ve made zero effort to reach out to us. Hillary’s VP choice is doubling down on her moderate platform and I think the people in this room are smart enough to realize once she gets into office, she’s just going to flip.”

Trump tweeted “hard to believe that Bernie Sanders has done such a complete fold,” and made another appeal to his supporters. “While Bernie has totally given up on his fight for the people, we welcome all voters who want a better future for our workers,” Trump tweeted.

Sanders rejects the idea that his supporters will vote for Trump. Trolling Trump’s acceptance nomination speech, Sanders tweeted last week, “Those who voted for me will not support Trump who has made bigotry and divisiveness the cornerstone of his campaign.”

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Poll: Trump gets bump following GOP convention

Recent polls show most Sanders supporters are ready to back Clinton over Trump. A Pew Research Center survey, conducted June 15-26, found that 85% of Democrats and Democratic-leaning voters who backed Sanders in the primary said they plan to vote for Clinton in the general election. Nine percent said they'll vote for Trump and 6% said they'll vote for another candidate or don’t know.

“In the end they’re going to vote for her,” said Patrick Murray, director of the Monmouth University Polling Institute. “The impact is on the level of enthusiasm. What they were hoping for is a clean convention with Sanders sending a very clear signal with his speech that ‘we’re all united behind Clinton.’ These email leaks just makes it harder for some of his supporters to do that in a very enthusiastic way.”

Contributing: John Bacon and Susan Page, USA TODAY

Follow @ngaudiano on Twitter.