CHICAGO (AP) — A refreshed Democratic Party is taking a look back while it moves forward as its convention opens Monday night, with President Joe Biden preparing a valedictory speech and delegates reveling in the newfound energy that followed Vice President Kamala Harris ' rise to the top of the ticket.

The national convention unfolding in Chicago this week holds particularly high stakes for Democrats. The party must finalize the unprecedented mid-campaign handoff from Biden to Harris and reintroduce the vice president to a divided country that's still making up its mind about her.

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

At morning meetings prior to Monday's primetime 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."

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 new generation of Democratic leaders, including Michigan Gov. Gretchen Whitmer and Pennsylvania Gov. Josh Shapiro, also spoke about the new "infusion" of energy at various delegation breakfasts.

Republican presidential nominee Donald Trump's campaign wasn't missing the opportunity to counterprogram. In its first daily gathering with media in Chicago on Monday, the campaign and its surrogates pointed to grocery cost increases and other economic woes they say will worsen if Harris is elected in November.

Preparing for November

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.

A potential distraction from the positivity of the convention 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 march and rally on the DNC was expected 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.

Much of the opening night programing will focus on Biden's record during his time in the White House.

"I think it's important for him to answer those age-old questions: What have you done for me lately and why bother to go out and vote?" said former Louisiana Rep. Cedric Richmond, a Biden adviser.

Biden will get his farewell Monday

Part of introducing Harris and Walz will be first giving a graceful exit to the incumbent president, who is slated to deliver the keynote 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 at his Trump debate.

By 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.

Trump has tried to inflame tensions over Biden's exit. He called Biden's Monday speaking slot "convention death valley," suggesting that the president would get lower ratings than speakers on other nights. And as he has for weeks, Trump described the convention itself as "rigged" because it was Biden, not Harris, who won 14 million primary votes and collected delegates state by state.

"She got no votes," Trump said.

A focus on Harris' firsts

The convention will lean into the party's potential to make history. Harris is vying to be the first woman, first Black woman and person of South Asian descent to reach the Oval Office.

"I wasn't sure I would see this particular moment in my lifetime, to see a Black woman who is now on the cusp of becoming our next president," said Illinois Lt. Gov. Juliana Stratton, one of the nation's highest-ranking Black female elected officials.

"I remember back in 2016 when we touched the glass ceiling, and the reaction of Republicans was just to start destroying the rights that got us there," Stratton said. "This is another chance."

Harris will aim to use the convention to take a share of credit for what she and Biden accomplished while also trying to show that she recognizes voters want more. Heading into Chicago, she unveiled the initial planks of her policy platform focused on addressing the bite of inflation and the costs of food, housing and childcare.

The presidential race is still very close

With precious few days remaining before early voting begins in some places, polls show a close race nationally and in battleground states including Pennsylvania, Michigan and Wisconsin. Trump still has advantages on how Americans view the two of them on core issues like the economy and immigration.

Terry McAuliffe, a former Virginia governor and longtime operative who will attend his 13th Democratic convention this week, warned that the euphoria Democrats have about Harris' ascension could obscure the true state of the campaign.

In addition to his team's daily news conferences in Chicago, the former president plans to go to a different swing state each day this week — starting with Pennsylvania, followed by Michigan, North Carolina, Arizona and Nevada by week's end.

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