Barack Obama can no longer stay on the sidelines as Kamala Harris threatens to jeopardize his unofficial fourth term and hand over control of the White House to Donald Trump - a potentially devastating verdict on the entire Obama legacy.

In a sign of how worried Obama is getting, the former president delivered an angry speech in the swing state of Pennsylvania full of gripes about Trump.

Trump gets under Obama's skin

Obama conceded that the race is "going to be tight " because many Americans are struggling financially. But Obama, who became a millionaire through his career in politics, said Trump is the wrong person to "shake things up."

"All he cares about is his ego and his money," Obama said.

Over the course of a 40-minute tirade, Obama alternated between his usual soaring appeals to "norms" and personal insults. The president who infamously bashed Americans "clinging" to religion took a swipe at Trump for selling Bibles and joked that he has never changed a diaper.

“He wants you to buy the word of God: Donald Trump edition. Got his name right there next to Matthew and Luke,” Obama said.

The normally slick Obama showed hints of jealousy as he attacked Trump's economic record. Obama claimed a "hazy memory" was causing Americans to give Trump credit for the prosperity that he inherited from his predecessor.

"It was my economy!" Obama claimed. "I had spent eight years cleaning up the mess that the Republicans had left me the last time. So just in case everybody has a hazy memory,” he added.

Obama lectures on masculinity

Earlier this year, Obama joined a Democrat-led conspiracy to pressure Joe Biden to end his re-election bid. As the race enters the home stretch, Democrats are growing worried that Harris is losing momentum.

Obama acknowledged those concerns before and during the rally, as he scolded men - particularly black men - who find Trump's macho personality appealing.

“I’m sorry gentlemen, I’ve noticed this, especially with some men who seem to think Trump’s behavior, the bullying and the putting people down, is a sign of strength,” Obama said. "And I am here to tell you that is not what real strength is.”

While Obama painted Harris as a refreshing change, the vice president told The View this week that there is nothing she would have done differently than President Joe Biden.

“There is not a thing that comes to mind," she said.