During his rally at the University of Pittsburgh, Mr. Obama admitted that the election would be “close” and noted that men appear to be particularly drawn to Donald Trump’s “bullying.”

“I’m sorry, gentlemen – this has particularly struck me with some men who seem to view Trump’s behavior of bullying and belittling people as a sign of strength,” he said. “I’m here to tell you that that is not what true strength is and never has been.”

In addition to urging voters to support the vice president, Mr. Obama sought to draw dividing lines between Ms. Harris and Trump.

He attacked the Republican candidate for spreading misinformation about the federal response to Hurricane Helene, criticized his policies on abortion, immigration and health care and compared his monologues to Fidel Castro, the late Cuban dictator.

Democrats hope Mr. Obama will give Ms. Harris a boost in the polls, which remain stalled after an initial surge after the vice president took over from Mr. Biden as the party’s nominee in July.

Mr. Obama’s initial failure to immediately endorse Ms. Harris after President Biden withdrew from the race fueled speculation about divisions with his former protégé, whose relationship dates back to 2004.

However, the former president dispelled the rumors by supporting Ms Harris in the following days, referring to her as “my girl”. Both Obamas gave speeches at the Democratic National Convention in August and were widely seen as outshining Ms. Harris.