PHILADELPHIA — Democrats who gleefully jeered Republican divisions last week awoke to a political mess of their own making Monday as party unity behind Hillary Clinton proved much harder to secure.

Gathering for their convention in Philadelphia, Democrats struggled to shake lingering bitterness among supporters of defeated rival Bernie Sanders and dealt with the aftermath of a leadership shakeup at the top.

The party announced Monday it would kick off its four-day spectacle with speeches from some of its most popular figures. Massachusetts Sen. Elizabeth Warren, a progressive favorite, would deliver the convention keynote. Sanders and first lady Michelle Obama will also take the stage.

The kickoff lineup had long been intended to appeal to the party’s restive liberal wing, but that task has become unexpectedly urgent. A trove of embarrassing leaked emails some said reveal an anti-Sanders bias at the supposedly neutral Democratic National Committee has ripped open some barely-heeled primary wound.

It was unclear whether the resignation Sunday of party chief Debbie Wasserman Schultz would be enough to unite the party behind Hillary Clinton.

How the emails were stolen hasn’t been confirmed, but the Clinton campaign pointed the finger at Russian hackers.

“There is a consensus among experts that it is indeed Russia that is behind this hack of the DNC,” Clinton campaign spokesman Brian Fallon told CNN Monday morning, arguing Russia was trying to influence the outcome of the U.S. election.

Trump dismissed the suggestion in a tweet: “The joke in town is that Russia leaked the disastrous DNC e-mails, which should never have been written (stupid), because Putin likes me.”

Republicans relished Democrats’ pre-convention tumult, just days after they bumped and bumbled through their convention, unsuccessfully trying to paper over their own division. GOP nominee Donald Trump declared on Twitter: “The Dems Convention is cracking up.”

Resistance to Clinton was on display during a demonstration Sunday as many thronged to a main thoroughfare and chanted, “Hell no, DNC, we won’t vote for Hillary.” Still many delegates, and Sanders himself, said they planned to fall in line, mindful of the Republican alternative.

Ohio’s Michael Skindell, a Sanders delegate, said Monday he plans to “strongly support the nominee of the party.”

DNC Vice Chair Donna Brazile, a veteran Democratic strategist who will lead the party on an interim basis after the convention, warned more leaked emails, and more apologies, could be coming.

For now, party leaders tried to make Wasserman Schultz’s exit as graceful as possible. Clinton and President Barack Obama both quickly praised the departed party chief.

At the Republican convention, Trump cast himself as the law-and-order candidate in a nation suffering under crime and hobbled by immigration, sticking to the gloom-and-doom theme. As he accepted the Republican nomination, Trump said: “The legacy of Hillary Clinton is death, destruction, terrorism and weakness.”

In return, Clinton seized upon what she called the “fear and the anger and the resentment” from Trump and Republicans, dismissing Trump’s declaration that only he could fix the problems that afflict the nation.

Clinton was due to campaign in Charlotte, North Carolina on Monday. Ahead of her speech to the VFW, Clinton secured the endorsement of retired Gen. John Allen, former Deputy Commander of U. S. Central Command and a former Commander of the International Security Assistance Force, overseeing NATO troops in Afghanistan.

“I have no doubt that she is the leader we need at this time to keep our country safe, and I trust her with that most sacred responsibility of commander in chief.”