The Democratic convention opened to chaotic scenes Monday, as rival supporters of Hillary Clinton and Bernie Sanders traded boos and jeers in a very public show of party disunity.
As polls showed Republican Donald Trump leading the race for the White House, Democrats meeting in Philadelphia to make Clinton the first woman presidential nominee from a major party were in disarray.
Sanders' supporters booed as a pastor leading the invocation prayer mentioned Clinton's name, setting the stage for a raucous chorus of cheers and jeers as successive speakers took to the podium.
The party is reeling from leaked Democratic National Committee emails which show nominally neutral party staff trying to undermine Sanders' insurgent campaign and questioning his Jewish faith.
Anti-secrecy website WikiLeaks at the weekend released nearly 20,000 emails from between January 2015 and May 2016, gleaned by hackers who apparently raided the accounts of seven DNC leaders.
The Federal Bureau of Investigation said it was investigating the "cyber intrusion," which the Clinton campaign blamed on Russian hackers bent on helping Trump.
The leftist Sanders lost to Clinton in the primary handily, but the scandal has angered his already embittered supporters, who believe the race was fixed.
The scandal led to the ouster of party chair Debbie Wasserman Schultz and an apology from party leaders.
"We want to offer a deep and sincere apology to Senator Sanders, his supporters, and the entire Democratic Party for the inexcusable remarks made over email," the Democratic National Committee said in a statement.
Trump the 'demagogue'
Twice on Monday, before his official evening address to the convention, Sanders appealed to supporters to help build party unity.
"We have got to defeat Donald Trump. We have got to elect Hillary Clinton and (running mate) Tim Kaine," Sanders told a gathering of his supporters hours before the opening of the four-day convention.
"Trump is a bully and a demagogue," he said. His call to support Clinton was nevertheless met with loud jeers.
He later sent a text message to supporters asking them not to protest on the floor of the convention as a "personal courtesy" to him. But that appeared to have little impact.
As the boos and chants of "Bernie! Bernie!" continued inside the convention hall, Sanders protesters outside tried to breach security barriers, leading to a handful of arrests.
"Clinton can't beat Trump. Period," said Michigan delegate Melissa Arab, a Sanders supporter.
"A ham sandwich could beat Trump and she's not going to beat him. If she's nominated, people are going to end up with somebody bad for president."
Many in the Sanders camp have voiced disappointment with Clinton's choice of centre-left running mate Kaine, a senator from Virginia, instead of a more liberal firebrand like senator Elizabeth Warren, who was also to speak yesterday.
Much now rides on Sanders' prime-time address later Monday, and those of Warren and First Lady Michelle Obama.
This was meant to be a valedictory event for Clinton.
Later this week, she will make history when she formally accepts the Democratic presidential nomination - the first woman to lead a major party's White House ticket.
But new polls showed Trump surging since his confirmation last week as the Republican presidential nominee, with a CNN poll putting him three points ahead of Clinton - a six-point post-convention bump.
Democratic delegates said it was time to come together.
"The stakes are too high. In the end it's going to be either Hillary Clinton or Donald Trump and it's not even a close call," said Paul Czisny, a 57-year-old delegate from Wisconsin who had supported Sanders.
The party is seeking to project a more unified message than the Republicans did at their convention last week in Cleveland, where fissures over Trump's candidacy were laid bare.
"The Democrats are in a total meltdown," Trump taunted on Twitter. "E-mails say the rigged system is alive & well!"
He later told supporters Clinton "worked very, very hard to rig the system. Little did she know that China, Russia, one of our many, many friends came in and hacked the hell out of us."
Trump has long sought to scoop up disaffected voters who feel Sanders - a self-described democratic socialist - was denied a fair shot at the nomination.
Clinton campaign manager Robby Mook on Monday sought to deflect questions about the row.
"Our party is coming together here to unify to elect Hillary Clinton and defeat Donald Trump, and that's what you're going to see today," he said.
Former president Bill Clinton is the star speaker at the convention Tuesday, while President Barack Obama and Vice President Joe Biden take the stage Wednesday.
Clinton got a modest boost Monday when former vice president Al Gore offered his endorsement.