Obama Returns to the D.N.C. With a Chance to Rescue His Legacy From Trump

Little wonder. Mr. Obama remains one of the most popular figures in American life. A new poll by Politico and Morning Consult found that 58 percent of Americans have a favorable view of the former president, the highest rating of any of the 28 political figures tested other than his wife, Michelle, who topped him with 60 percent. Mr. Biden, by contrast, was seen favorably by 46 percent and Mr. Trump by 39 percent.

Even so, history has shown that presidents cannot always transfer their personal popularity to others, as Mr. Obama was reminded in 2016. And while he has deep affection for Mr. Biden, advisers say the former president harbors his own concerns about his former vice president’s chances this year. He had originally picked Mr. Biden as his running mate in 2008 as a governing partner, not as a putative successor, and he never groomed any younger figure to follow, leaving the party in 2016 with weathered leadership.

That has left many in his party anxious for him to play the bigger role that until lately he has resisted. Mr. Obama has been reluctant to fully engage with Mr. Trump or the campaign, only occasionally emerging from his Washington home where he is still writing his overdue memoir to take on the current president, as he did energetically during the 2018 midterm elections and as he had begun to do so this year.

“We have no moral voice today — no Martin Luther King, no Nelson Mandela, no John Lewis, no Eleanor Roosevelt,” said Susan Dunn, a presidential historian at Williams College. “Obama could retake that moral role — and not just reclaim his own legacy and not just denounce Trump for reversing all of Obama’s policies and achievements. He’d have to play a more active role in American life as a voice of moderation and decency.”

Mr. Obama’s determination to see Mr. Trump defeated may be as powerful, or even more so, than his desire to elevate Mr. Biden. After all, Mr. Trump spent years peddling the lie that Mr. Obama might have born in Africa and has spent much of his presidency unraveling whatever he could of Mr. Obama’s legacy. In recent months, the president has twisted the facts to accuse the former president of “spying” on his 2016 campaign and even suggested his predecessor had committed “treason,” a crime that carries the death penalty.

But Mr. Obama was not planning to dwell on that in his convention speech, veering away from personalizing the confrontation between presidents, aides said on Wednesday. Instead, they said, he planned to use his platform to validate Mr. Biden and his running mate, Senator Kamala Harris of California, assail Mr. Trump’s handling of the coronavirus and economy, and argue that democracy is on the line.