President Biden and first lady to make 'strong case' to elect Harris at DNC on Monday night

President Joe Biden and First Lady Jill Biden will speak at the Democratic National Convention in Chicago on Monday night, a senior DNCC spokesperson confirmed.

Their speeches will "make a strong case" to elect Vice President Kamala Harris, the spokesperson said.

"We are so excited to honor and celebrate the President's lifetime of service and unmatched legacy," the statement added.

Aides say Biden will address "how in the battle for the soul of America, we’ve ensured democracy prevailed, democracy delivered, and now with Kamala Harris and Tim Walz, we must ensure democracy is preserved."

Harris, who is on a campaign swing this weekend, will arrive in Chicago from Pennsylvania on Sunday night, and is expected to join the "tributes to Biden" on Monday. She'll then go up to Milwaukee for a rally on Tuesday.

The Democratic National Convention is set to begin Monday in Chicago -- during which Democratic Party delegates are set to support Harris and her running mate, Minnesota Gov. Tim Walz, after their unconventional path to the party's nomination.

During the four-day convention, Democratic heavyweights are set to rally behind Harris, who was officially certified as the Democratic presidential nominee earlier this month after getting the vast majority of delegate votes in a virtual roll call.

Harris' path to the DNC has been an unorthodox and truncated one after President Joe Biden announced he was leaving the 2024 race and endorsed the vice president for the job on July 21.

ABC News' Molly Nagle contributed to this report.