Former President Barack Obama, the popular elder statesman of the Democratic Party, will stump for Vice President Kamala Harris in battleground states in the month before Election Day, beginning with a campaign stop next Thursday in Pittsburgh.

He is set to crisscross the country for events in battleground states in the final 27 days before the election.

Mr. Obama, the first Black president, headlined Night 2 of the Democratic nominating convention in August. He symbolically passed the torch to Ms. Harris — a daughter of Jamaican and Indian immigrants — as the inheritor of his political movement and made the case that Ms. Harris’s candidacy was an extension of his own.

In his speech, he said Ms. Harris “won’t be focused on her problems — she’ll be focused on yours. As president, she won’t just cater to her own supporters, punish those who refuse to kiss the ring or bend the knee. She’ll work on behalf of every American.”

Now, he’s joining the final push to deliver the vice president a victory, starting with perhaps the most consequential battleground state of the election — Pennsylvania. Mr. Obama had warned in his convention speech that Ms. Harris’s victory was not assured, and urged Democrats to seek an overwhelming victory against former President Donald J. Trump.

“It’s up to all of us to fight for the America we believe in,” Mr. Obama said at the convention in August. “And make no mistake: It will be a fight.”

Ms. Harris, as she took over the Democrats’ presidential campaign after President Biden stepped aside this summer, added a number of former Obama advisers to her team, including David Plouffe, who managed Mr. Obama’s first presidential bid.