CHICAGO (AP) — A refreshed Democratic Party will gather Monday night for a valedictory speech from President Joe Biden, whose decision to end his reelection bid released newfound energy with Vice President Kamala Harris ' rise to the top of the ticket.

The Democratic National Convention that began Monday in Chicago holds particularly high stakes for the party. It must finalize the unprecedented mid-campaign handoff from Biden to Harris and reintroduce the vice president to a divided country that is viewing her more positively but still making up its mind about the election.

If successful, Democrats will slingshot Harris toward an faceoff with Republican Donald Trump, whose comeback bid for the White House is viewed by Democrats as an existential threat. But a false step could hobble Harris at a moment when her candidacy has been enjoying a burst of money, momentum and even joy.

Beyond the convention's celebrations, real questions loom about the depth of Harris' newfound support, the breadth of her coalition and the strength of her movement. Not even a month ago, Democrats were deeply divided over foreign policy, political strategy and Biden himself, who was holding on after a disastrous debate by claiming he had a better chance than any other Democrat — including Harris — of beating Trump.

At morning meetings prior to Monday's prime-time programming, convention delegates were dressed head to toe in merchandise celebrating Harris and her running mate, Minnesota Gov. Tim Walz. Some wore the vice president's face on their scarves or her slogans on graphic tees.

Walz suggested at a meeting of the Hispanic Caucus that Harris had reset the race.

"People don't just want to vote against something. They want to vote for something," he said. "Kamala Harris has given you something to vote for."

Part of introducing Harris and Walz will be first giving a graceful exit to the incumbent president, who is slated to deliver the main address Monday.

The Democratic Party probably would have been in a far worse state if Biden had continued to cling to the nomination. He faced growing concerns about his mental and physical acuity after struggling to complete sentences during his debate against Trump.

After deciding to step aside and endorse Harris, Biden will instead receive a hero's welcome in his final turn in the spotlight 52 years after being elected to the Senate from Delaware.

At a breakfast hosted by the Florida delegation, a party volunteer pulled out a suitcase and began to hand out replicas of Biden's famous aviator sunglasses.

"Joe Biden made a selfless, heroic decision, and it'll be awesome to celebrate him tonight," Democratic Rep. Kathy Castor of Florida told The Associated Press. "And then we're going to look to the future and pivot."

A potential distraction will be thousands of protesters descending on Chicago to decry the Biden-Harris administration's support for Israel's war against Hamas in Gaza.

A few thousand people marched toward the United Center, site of the DNC, on Monday afternoon. And a group that called itself the Abandon Biden movement held an event to rebrand itself as Abandon Harris. The group argued the vice president's inability to differentiate herself from Biden's handling of the war was not acceptable.

Harris' allies hope the pro-Palestinian protesters will not overshadow the official program, which features a slate of current and former Democratic stars, plus what organizers describe as "everyday people."

Among the speakers: United Auto Workers President Shawn Fain; Hillary Clinton; Reps. Grace Meng, Jamie Raskin and Jasmine Crockett; Sens. Chris Coons and Raphael Warnock; and Kentucky Gov. Andy Beshear.

Also expected to perform are musicians James Taylor, Jason Isbell and Mickey Guyton.

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Barrow reported from Atlanta. Associated Press writers Will Weissert in Chicago, Ali Swenson and Michelle L. Price in New York and Chris Megerian in Washington contributed to this report.