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 Hornsbrook, 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

The attention on Day 2 of the Democrats’ gathering shifts from celebrating President Joe Biden to prime-time speeches from former President Barack Obama and former first lady Michelle Obama. They'll help pass the party torch to Kamala Harris.

The convention will also hold a ceremonial roll call to nominate Harris, which follows the party's virtual process doing so earlier this month. Harris officially had the vast majority of delegate votes needed to secure her nomination when that process ended on Aug. 6.

It’s expected that California Gov. Gavin Newsom and Harris’ home state delegation will cast the vote putting her over the top.