The Democratic National Convention’s first day in Philadelphia was supposed to be a grand demonstration of party unity and shared determination to defeat Donald Trump.

But delegates in attendance didn’t get the message. Instead, just moments after the convention officially opened, it devolved into internecine warfare.

Though Bernie Sanders is scheduled to speak later in support of Hillary Clinton, after endorsing her earlier this month, there seems to still be some lingering resentment. Even the promise of a speech from Elizabeth Warren, a progressive hero to many of Sanders’s supporters, didn’t seem to be enough to placate Sanders die-hards as the convention kicked off Monday afternoon.

Every time Hillary Clinton’s name was mentioned at the outset, delegates booed loudly from the floor:

Bernie supporters from Michigan boo Hillary as Cummings speak. #DemsInPhilly pic.twitter.com/8V9IiL5PjA — Emma Loop (@LoopEmma) July 25, 2016

This thing is off the rails. Every time @HillaryClinton named massive boos cry out. Can't even hear Marcia Fudge in the arena. #DemsInPhilly — Domenico Montanaro (@DomenicoNPR) July 25, 2016

Pattern on the floor: mentions of Hillary draw more cheers than boos, but there are lots of boos, and Bernie fans cheer longer than hers. — Josh Barro (@jbarro) July 25, 2016

Pretty obvious down here on the floor that a significant % of the Bernie delegates are unhappy. And vocal. #DNC2016 — Scot Lehigh (@GlobeScotLehigh) July 25, 2016

The "lock her up" chant — a favorite of delegates to the Republican National Convention that was heavily criticized — has made an appearance at the Democratic convention as well:

Bernie delegates from CA chant "Lock her up" — Betsy Woodruff (@woodruffbets) July 25, 2016

Sanders himself tried to calm the chaos, asking his supporters to corral the demonstrations and to stop them from unfolding:

After rowdy day, Sanders sends text to supporters:"I ask you as a personal courtesy to me to not engage in any kind of protest on the floor" — Nancy Cordes (@nancycordes) July 25, 2016

But as several observers pointed out, Sanders had encouraged his supporters to believe that he could win the nomination — and now is struggling to wind them down now that he’s fallen in line behind Clinton:

Extraordinary watching Sanders plead with his supporters to come back down to earth, after months of fueling unlikely victory scenarios. — Nick Confessore (@nickconfessore) July 25, 2016

Iowa delegate @chris_laursen: "Bernie basically fed us a bunch of Mountain Dew and now he wants us to go to bed. It’s not going to happen." — Jason Noble (@jasonnobleDMR) July 25, 2016

All in all, between the growing protests outside and the chaos on the convention floor, Philadelphia is offering the spectacle of a divided party that the Republican convention in Cleveland did not. Even when boos broke out during Sen. Ted Cruz’s speech to the RNC, they were in favor of the party’s nominee: