New Democratic ticket? Gov. Roy Cooper joins VP Kamala Harris at a campaign stop in N.C.

North Carolina Gov. Roy Cooper fired up the crowd before Vice President Kamala Harris stumped in Fayetteville on Thursday.

Mr. Cooper, a Democrat completing his second term, said former President Donald Trump would give wealthy people “the breaks” while working people “get the shaft.”

His voice rising, the governor said Mr. Trump is a convicted felon who would erode gains in health coverage and clamp down on abortion rights across the country.

“Do we want Donald Trump’s America?” Mr. Cooper said.

“No!” the crowd shouted back.

Mr. Cooper, 67, is among a crop of potential running mates for Ms. Harris, 59, if she has to replace President Biden at the top of the ticket due to concerns about his advanced age of 81 and cognitive abilities.

Pundits also have floated Gov. Josh Shapiro, a popular Democrat in Pennsylvania.

Mr. Harris said she and Mr. Cooper go way back, pointing to their simultaneous service as attorneys general in California and North Carolina.

“I’ve known him for almost two decades, and he is an extraordinary leader,” Ms. Harris said.

Mr. Biden, who is sick with COVID-19, insists he isn’t going anywhere but faces a tide of calls to step aside, potentially forcing his hand.

For now, Democratic allies are acknowledging the status quo ticket of Mr. Biden and Ms. Harris.

“I know she is a fighter, I know she gets the job done, and I know that she and Joe Biden need four more years to finish the job,” Mr. Cooper said.

Mr. Cooper is a Democratic success story in North Carolina, a swing state worth 16 electoral votes.

Still, North Carolina has eluded Democrats in recent presidential elections — despite changing demographics, including a tide of arrivals from the Northeast, that should have favored the party.

A North Carolina win would provide insurance for Democrats if they forfeit any swing states they won in 2020.

During her speech, Ms. Harris said her GOP vice presidential rival, Sen. J.D. Vance of Ohio, outlined a compelling life story at the GOP convention but hid key details of the Republican agenda. She says the GOP ticket is a threat to abortion rights and programs like Social Security and Medicare.

Ms. Harris also took Mr. Trump and Mr. Vance to task for using unity as their theme in Milwaukee.

“You need to do more than just use the word,” she said. “You cannot claim you stand for unity if you are pushing an agenda that deprives whole groups of Americans of basic freedoms, opportunity and dignity.”

Polls show Ms. Harris fares slightly better than Mr. Biden in hypothetical matchups with Mr. Trump. However, she faces political vulnerabilities, including a failure to complete a lengthy to-do list from Mr. Biden, such as shoring up voting rights and stopping the flow of migrants coming into the U.S.