Biden’s Goodbye to Politics Will Begin in Earnest With His Convention Speech

President Biden’s goodbye to a half century in national politics will begin in earnest on Monday.

When he takes the stage at the Democratic National Convention in Chicago that evening, Mr. Biden will establish his time in office and his political legacy as the foundation for the candidacy of Vice President Kamala Harris, the new Democratic nominee.

According to Biden aides who previewed the themes of the president’s remarks, he will say that she is the best person to finish a campaign he started — one that remains rooted in protecting democratic ideals and preventing a second term for former President Donald J. Trump, the Republican nominee. The aides spoke on condition of anonymity because they were not authorized to detail the plans.

It will be a bittersweet moment for Mr. Biden, who left the race and turned the keys of his campaign over to Ms. Harris less than a month ago. Since then, she has headlined packed rallies and delivered forceful campaign speeches, and the president has largely receded from center stage.

But Mr. Biden, who is supportive of Ms. Harris and appreciates the momentum around her, the aides said, plans to ramp up his campaign schedule. He has also been focused on sealing up his legacy as a one-term president — but one who pulled the nation out of an economic spiral during the coronavirus pandemic, a point he will make in his speech.

On Friday, Mr. Biden left Washington for Camp David for the weekend; he was scheduled to workshop his speech with Mike Donilon, a close adviser, and Vinay Reddy, his chief speechwriter.

In his speech, the president will also frame Ms. Harris’s campaign as continuing policies and ideals he has long championed. Mr. Biden’s remarks will make the case that “democracy prevailed” with his election in 2020. A win for Ms. Harris and her running mate, Gov. Tim Walz of Minnesota, in November will mean that “democracy is preserved.”

Before Mr. Biden speaks, the first lady, Jill Biden, is scheduled to deliver brief remarks. Dr. Biden’s time in office was spent supporting cancer-research initiatives and military families. She also lent her platform to many of the administration’s broader efforts, including a coronavirus vaccine campaign, and much of her time was spent on the campaign trail and at fund-raising events in support of her husband’s re-election effort.

The Biden aides said that organizers of the convention would work to recognize the president’s legacy throughout the week. Delegates will receive goody bags in which officials with the United Center, the host venue, included coffee beans for a “cup of Joe” as a tribute to Mr. Biden.

Several Biden family members are expected to join the president and first lady at the convention on Monday. The family is not expected to stay throughout the week. Mr. Biden wants to speak and then hand off the convention to Ms. Harris and Mr. Walz, the aides said. The digital banners in the convention that day will call back to Mr. Biden by displaying messages like “Spread the faith” and “History is in your hands” before going dark and converting to messages associated with Ms. Harris.

Other speakers on Monday include Hillary Clinton, the 2016 Democratic nominee. Her husband, former President Bill Clinton, is scheduled to speak on Wednesday, according to a person familiar with their schedule.

The rest of Mr. Biden’s time in office, the Biden aides said, would be spent working to cut costs and implement legislation, and would include a packed foreign policy agenda.