By John Whitesides and Luciana Lopez
PHILADELPHIA (Reuters) - Supporters of Bernie Sanders disrupted the first day of the Democratic convention on Monday, repeatedly chanting and booing mentions of Hillary Clinton's name as the party's hopes for a show of unity dissolved into frequent chaos.
Speakers in the convention's first hours struggled to carry out business as angry Sanders supporters roared their disapproval, drawing a deafening response from Clinton delegates.
"We're all Democrats and we need to act like it," U.S. Representative Marcia Fudge of Ohio, the convention's chairwoman, shouted over the uproar.
Earlier in the day, Sanders drew jeers from his own supporters when he urged his delegates to back the White House bid of his former rival, Clinton, and focus on defeating Republican Donald Trump in the Nov. 8 presidential election.
"We want Bernie," they shouted in a show of anger at both Clinton's victory in the race for the Democratic nomination and emails leaked on Friday suggesting the party leadership had tried to sabotage Sanders' insurgent campaign.
For months, Sanders, 74, a U.S. senator from Vermont, mounted an unexpectedly tough challenge to Clinton, 68, a former secretary of state, who this week will become the first woman nominated for president by a major U.S. political party.
The scenes of booing in Philadelphia were a setback to Democratic officials' attempts to present the gathering as a smoothly run show of party unity in contrast to the volatile campaign of Republican nominee Trump.
Sanders tried to head off the disruptions, sending an email to delegates as the convention opened urging them to refrain from interrupting the proceedings.
"Our credibility as a movement will be damaged by booing, turning of backs, walking out or other similar displays. That's what the corporate media wants. That's what Donald Trump wants," Sanders said in the email.
Trump gloated at the Democrats' opening day disorder.
"Wow, the Republican Convention went so smoothly compared to the Dems total mess," he wrote on Twitter.
The Democratic National Committee issued "a deep and sincere apology to Senator Sanders, his supporters, and the entire Democratic Party for the inexcusable remarks made over email" and said it would take action to ensure it never happens again.
Democratic National Committee Chairwoman Debbie Wasserman Schultz resigned effective at the end of the convention over the email flap. At a morning gathering of Florida delegates, Sanders supporters booed Wasserman Schultz, who they accuse of trying to sabotage the campaign of the democratic socialist.
Sanders, speaking later to his delegates in Philadelphia, drew jeers and catcalls when he urged supporters to help defeat Trump by backing Clinton and her vice presidential running mate, U.S. Senator Tim Kaine of Virginia.
"Brothers and sisters, this is the real world that we live in," he said, adding: "Trump is a bully and a demagogue."
Members of the crowd screamed back: “So is Hillary.” "She stole the election!" someone else shouted.
Sanders complained bitterly during the primary that the party leadership was working against him. Some of his backers are reluctant to get behind Clinton, seeing her as a member of the Washington political elite who pays lip service to their goals of reining in Wall Street and eradicating income inequality.
Speakers pleaded for unity among the competing supporters. Diane Russell, a Sanders delegate from Maine, said the party had to come together to beat Trump.
"Whether you support Bernie Sanders or Hillary Clinton, we're all in this together," she said.
U.S. Senator Jeff Merkley of Oregon, the only senator to endorse Sanders, said supporters of the two former rivals had plenty in common.
"Whether you spent this year feeling the Bern or you spent this year ready for Hillary, all of us are ready for an America that rejects discrimination and embraces diversity, that celebrates voter empowerment not voter suppression, that creates opportunity for all of us, not just the lucky few," he said.
While Sanders has endorsed Clinton, the former first lady faces a difficult task winning over his backers in the fight against Trump. The New York businessman pulled ahead in at least one opinion poll on Monday, after lagging Clinton in most national surveys for months.
A CNN/ORC opinion poll gave Trump a 48 percent to 45 percent lead over Clinton in a two-way presidential contest.
Trump was formally nominated for president at a chaotic Republican convention in Cleveland last week.
Sanders was among those due to speak on the first evening of the Democratic convention. Other scheduled speakers included President Barack Obama's wife, first lady Michelle Obama.
'DEMOCRACY IS MESSY'
Ed Mullen, 49, a delegate from Illinois, said he supported Sanders but would vote for Clinton in November. He said the protesters at the convention had a right to stay.
"Democracy is messy, people have disputes with how the DNC has managed this campaign," Mullen said.
Wasserman Schultz, a Florida congresswoman, was the focus of anger from liberal Democrats over some 19,000 DNC emails that were leaked by the WikiLeaks website that showed the party establishment working to undermine Sanders.
The cache of leaked emails disclosed that DNC officials explored ways to undercut Sanders' insurgent presidential campaign, including raising questions about whether Sanders, who is Jewish, was an atheist.
Sanders supporters were already dismayed last week when Clinton passed over liberal favorites like U.S. Senator Elizabeth Warren of Massachusetts to select the more moderate Kaine as her running mate.
The Clinton camp questioned whether Russians may have had a hand in the hack attack on the party's emails in an effort to help Trump, who has exchanged words of praise with Russian President Vladimir Putin. Republicans dismissed the suggestion as absurd.
The FBI said on Monday it would investigate the nature and scope of the hack.
(Additional reporting by Jonathan Allen, Amy Tennery, Alana Wise, Emily Stephenson, Erik Tavcar; Writing by John Whitesides and Alistair Bell; Editing by Frances Kerry and Peter Cooney)