PHILADELPHIA -- Hillary Clinton's campaign scrambled to extinguish a political firestorm over embarrassing hacked emails Monday, hoping a high-wattage line-up of speakers, including first lady Michelle Obama and liberal favorite Bernie Sanders, would overshadow party infighting on the Democratic convention's opening night.
Clinton escaped one potentially ugly moment when outgoing party chair Debbie Wasserman Schultz announced she would not take the stage. The Florida congresswoman was angrily heckled by her own home-state delegation Monday morning, and Democratic officials feared a similar scene in front of a far bigger TV audience.
Wasserman Schultz is leaving her post following the publication of thousands of emails suggesting the Democratic National Committee favored Clinton during her primary contest with Sanders, despite vowing to remain neutral. Sanders and his supporters have long argued that the party was on the side of the former secretary of state.
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As the convention began in sweltering Philadelphia, the DNC released a statement apologizing to Sanders and his supporters "for the inexcusable remarks made over email." The party said the comments do not reflect the party's values or commitment to neutrality in the primary process.
The statement was signed by DNC leaders, though Wasserman Schultz's name was notably absent.
There were some signs that Sanders' supporters did not plan to go quietly. Even during the invocation, chants of "Bernie" echoed through the arena.
For Clinton, it was a turbulent start to a historic four-day gathering that will culminate in the nomination of the first woman to lead a major U.S. political party. It also sapped some of Clinton's energy coming out of Republican Donald Trump's chaotic convention last week and the well-received rollout Saturday of her running mate, Virginia Sen. Tim Kaine.
Sanders will play a crucial role in determining whether Clinton can calm the tensions. He greeted his loyal delegates ahead of his convention address Monday, imploring them to help him elect Clinton and prevent Trump from winning the White House, though he spent little time making a robust case for his former rival.
The frustration some Sanders' supporters still have with Clinton -- a candidate they see as entrenched in a political system they distrust --was evident, with the crowd breaking into a chorus of boos.
"Brothers and sisters, this is the real world that we live in," Sanders said as he tried to quiet the crowd. "Trump is a bully and a demagogue."
Sanders was the closing speaker on a night also featuring Mrs. Obama, who remains a wildly popular figure; New Jersey Sen. Cory Booker, a young black lawmaker and rising Democratic star, and Massachusetts Sen. Elizabeth Warren, a favorite of liberals and one of the party's toughest critics of Trump.
Clinton is promising a stark contrast to last week's Republican gathering, an often chaotic affair that featured a heavy dose of pessimism about the economy and national security.
"I don't see how you run for president of the United States if you spend all your time trash-talking the United States," she told supporters. "We're going to have a convention this week that highlights success stories."
The controversy over some 19,000 leaked DNC emails, however, threatened to complicate those plans. The correspondence, posted by WikiLeaks over the weekend, showed top officials at the supposedly neutral DNC favoring Clinton over Sanders in the presidential primaries.
Clinton campaign officials blamed the hack, which is now being investigated by the FBI, on Russian military intelligence agencies. The campaign also accused Moscow of trying to meddle in the U.S. election and help Trump, who has said he might not necessarily defend NATO allies if they are attacked by Russia.
"We don't have information right now about that, but what we have is a kind of bromance going on between Vladimir Putin and Trump which is distinct from this leak," Clinton adviser John Podesta said in an MSNBC interview.
Trump dismissed the suggestion in a tweet: "The joke in town is that Russia leaked the disastrous DNC emails, which should never have been written (stupid), because Putin likes me."
A cybersecurity firm the Democrats employed found traces of at least two sophisticated hacking groups on their network -- both of which have ties to the Russian government. Those hackers took at least a year's worth of detailed chats, emails and research on Trump, according to a person knowledgeable of the breach who wasn't authorized to speak publicly about the matter.
Regardless of the origins of the hack, it was Wasserman Schultz who bore the brunt of the political fallout. Long a controversial figure, by Sunday afternoon she announced she would resign.
But the congresswoman had hoped to still fulfill her official duties in Philadelphia, taking the stage to gavel the convention in and out -- scenarios that became untenable by midday Monday.
"I have decided that in the interest of making sure that we can start the Democratic convention on a high note that I am not going to gavel in the convention," she told a newspaper in her south Florida district, the Sun-Sentinel.
For Sanders' supporters, it was a high-profile victory. But it did little to temper their ongoing concerns about the woman at the top of the Democratic ticket.
"We are all scared of Donald Trump, but we also have misgivings about Hillary," said Bruce Fealk, a Sanders delegate from Michigan.
Sanders supporters protest
Police took 40 people into custody outside the Democratic convention Monday evening after several hundred Bernie Sanders supporters and other demonstrators converged in the sweltering heat, chanting "Nominate Sanders or lose in November!" and "Hey, hey, ho, ho, the DNC has got to go!"
The marchers set out from City Hall and made their way some 4 miles down Broad Street, gathering near the Wells Fargo Center around the time the convention was gaveled to order.
Protesters tried to climb over police barricades at the edge of the security zone surrounding the convention, and police Chief Inspector Joseph Sullivan said 40 people were taken into custody. As tensions mounted, police moved metal fences into place and closed the nearest subway station to arriving trains.
Protesters carried signs that read, "Never Hillary," "Just Go to Jail Hillary" and "You Lost Me at Hillary."
One of the marchers who made their way toward the convention hall, Destine Madu, of Maplewood, New Jersey, said it doesn't matter if Sanders is calling on his backers to support Hillary Clinton.
"He's like a Moses," she said. "He led us to the promised land."
The anger on the streets reflected the widening rift inside the Democratic Party and the convention hall itself between Sanders' supporters and Clinton's.
On Sunday, Debbie Wasserman Schultz resigned as Democratic Party chairwoman over leaked emails suggesting the supposedly neutral Democratic National Committee played favorites during the primaries by siding with Clinton and bad-mouthing Sanders.
The protests took shape amid a punishing heat wave, with oppressive humidity and temperatures in the mid-90s, along with the possibility of severe thunderstorms in the evening. The Fire Department handed out bottled water, and a few protesters were treated for heat-related problems.
About 100 Sanders supporters made their way into Philadelphia by marching across the Ben Franklin Bridge from Camden, New Jersey. Among them was Jim Glidden, a salesman from Batavia, New York. He carried a big sign saying the DNC stands for "Dishonest Nefarious Corrupt."
"Only one guy is telling the truth out there," he said, referring to Sanders. "And the DNC shut him up with lies and cheating."
Another participant in the bridge march, Deborah Armstrong, of Spokane, Washington, said she and her husband went bankrupt because of his health problems, which required a heart transplant.
"I'm Bernie or bust," she said. "I'm not going to have Trump held up to our head like a gun."
The demonstrators espoused a variety of causes, including economic justice, socialism and marijuana legalization. With Sanders out of the race, some of them were backing Green Party candidate Jill Stein.
Tensions rose when about 50 marchers sat down on Broad Street and refused to move unless the Mississippi state flag with the Confederate emblem was taken down from a lamppost. The flags of all 50 states fly from light poles on the street.
Two officers stood in front of the lamppost, not allowing anyone to climb it, as hecklers jeered: "Think for yourself. Be a real man."
City officials later removed the flag.
"The Confederate flag raises strong feelings in our city and across the country," said Brian Abernathy, Philadelphia's first deputy managing director.
The four-day convention is far removed from City Hall and the skyscrapers of Center City.
In contrast, the Republican convention last week in Cleveland was held in a bustling part of the city. A heavy police presence and fewer than expected protesters helped authorities maintain order. Only about two dozen arrests were made.
Associated Press writers Kathleen Hennessey, Catherine Lucey and Kathleen Ronayne in Philadelphia, Lisa Lerer in Charlotte, North Carolina, and Jeff Karoub in Detroit contributed to this report.