DNC 2024 Day 2 live updates: 'Yes, she can': Obama endorses Harris, blasts Trump

For the first half of 2024, a huge question for the Biden campaign was whether he would lose a critical amount of support with key blocs of voters that supported him in 2020, such as Black voters and young voters. Now, however, Harris is running instead, and her coalition isn’t necessarily the same as Biden’s.

In a new article, 538 Senior Researcher Mary Radcliffe took a deep dive into national polls to answer the question of who, exactly, makes up the Harris coalition. She also compared Harris’ polling numbers among various racial, gender and age groups to Biden’s. It turns out that Harris has shored up a lot of Biden’s weaknesses -- and it’s pretty surprising which group she is outpacing him with by the most.

—538’s Nathaniel Rakich

On Tuesday night, former President Barack Obama gives a highly anticipated speech in which he is expected to make a forceful case for electing Harris. It won’t be the first time that Obama spoke glowingly of Harris -- in fact, he has gotten in trouble for it before. Back in 2013, he spoke at a fundraiser in California that Harris attended and said of the then-California attorney general, “She is brilliant and she is dedicated and she is tough, and she is exactly what you'd want in anybody who is administering the law, and making sure that everybody is getting a fair shake. She also happens to be by far the best-looking attorney general in the country.” The comment on Harris’s looks sparked a backlash for being sexist and inappropriate, and he apologized the next day.

—538’s Nathaniel Rakich

When former President Barack Obama and former first lady Michelle Obama speak at the DNC on Tuesday, they will highlight their friendship with Harris that they say goes back 20 years, according to a source familiar.

The Obamas have been in regular touch with Harris over the years, providing counsel and being a sounding board, too, the source said. Over the last few months in particular, the Obamas have been in close contact with the vice president and supported her campaign in any way they are able, the source said.

Their remarks on Tuesday will turn the page from the Biden administration and focus on how Harris and Walz are the leaders the country needs right out, the source said.

The source highlighted how the Obamas have campaigned for Harris and worked to energize young voters.

-ABC News' MaryAlice Parks

The DNC will start its programming half an hour earlier than originally planned on Tuesday after Monday's program had a delayed start that pushed President Joe Biden's speech past prime time and cut short his farewell.

"We had so much energy and enthusiasm for our president, our ticket, from our speakers and the audience reaction that I recognize that did put us a little bit behind schedule, but we are working with -- we made some real-time adjustments last night to ensure we could get to what the delegates and the viewers really came for, which, of course, is President Biden," Alex Hornbrook, the executive director of the convention, told reporters this morning.

"And we're working with our speakers and making some other adjustments for this evening, including beginning at 5:30 to make sure that we stay on track for that tonight," he added.

-ABC News' Fritz Farrow