US Vice-President Kamala Harris has done her first major interview with a journalist since she replaced Joe Biden as the Democratic nominee.

Harris and her running mate, Minnesota Governor Tim Walz, sat down with CNN's Dana Bash for 18 minutes to discuss their sudden elevation on the Democratic ticket.

The interview was seen as a major test for Harris, who has stumbled in the past in similar situations.

Back in 2021, for example, she was widely criticised after she got into a strange back-and-forth with NBC's Lester Holt about why she hadn't visited the US-Mexico border, despite being tasked with a leading role on immigration.

"You haven't been to the border," Holt said.

"And I haven't been to Europe," Harris replied.

"And I mean, I don't understand the point that you're making. I'm not discounting the importance of the border."

So the stakes of the interview on CNN on Thursday, local time, were high as the Harris-Walz campaign sought to fight the narrative that they might not be ready for the highest office in the land.

These were the biggest moments from the interview.

Harris gets off to a slow start 

Harris has had a most unusual rise to the top of the ticket.

In case you've forgotten, President Joe Biden won the Democratic nomination with Harris as his running mate.

But after a calamitous debate against Republican challenger Donald Trump in June that raised questions about his fitness for the job, he eventually bowed to party pressure and stepped aside for his vice-president.

Harris has had a charmed run ever since, with national polls showing her catching up to Trump and the party faithful cheering her on at the Democratic National Convention (DNC) earlier this month.

Biden has given his full-throated endorsement to Harris, describing the moment he chose her as his VP as the best decision of his presidency.

But Bash asked Harris some tough questions about whether she ever had concerns about Biden's mental acuity or age during their years together in the White House.

"He cares so deeply about the American people. He is so smart and loyal to the American people. And I have spent hours upon hours with him, be it in the Oval Office or the Situation Room," she said.

"He has the intelligence, the commitment and the judgement and disposition that I think the American people deserve in their president."

While there were no major flubs during her interview, this wasn't the energetic, commanding and yes, joyful, Harris we saw at the DNC. 

Given there's been a month to prepare for this interview, Harris's team would have wanted a strong start. 

The first question from Bash was fairly straight forward and obvious. 

"What would you do on day one in the White House?" she asked. 

"First and foremost, one of my highest priorities, is to do what we can to support and strengthen the middle class," Harris responded. 

But before offering any real details, she then attempted to turn the attention to Trump. 

Bash attempted to get her back on track. 

"So what would you do day one?" she prompted. 

Walz's dad status gives him his most awkward and his most moving moments

Harris passed over several other much more famous Democrats to pick Walz as her running mate.

The Minnesota governor has lit the internet on fire by combining folksy charm, a nice dad energy, and devastating attack lines on Trump.

But the Republican Party has sought to paint him as being dishonest on multiple fronts.

They accused him of embellishing his record of service in the National Guard, lying about a youthful drunk driving arrest, and misrepresenting his and his wife's infertility treatments.

When questioned by Bash, he admitted he mixed up in-vitro fertilisation (IVF) with intra-uterine insemination — the treatment used by the Walzes to have both their children — but said it wasn't intentional.

"I certainly own my mistakes when I make them," he said.

"The one thing I'll tell you is I wished in this country, we wouldn't have to do this. I spoke about our infertility issues because it's hell, and families know this."

Bash also asked Walz about one of the most viral moments of the DNC earlier this month, when his son Gus was moved to tears as he watched his dad accept the nomination to be Harris's running mate.

"As a father, I could not have ever imagined that I would be grateful for so many reasons to be on this ticket," he said as he fought back tears.

"But it was just such a visceral, emotional moment that I'm grateful I got to experience it, and I'm so proud of him. I'm proud of him, I'm proud of [daughter[ Hope. I'm proud of [wife] Gwen, a wonderful mother, and these are great kids."

Harris addresses two of her trickiest policy points

During the interview, Harris had to address two of the most difficult and divisive issues for the Democratic Party: immigration and the war in Gaza.

One of the most pointed and repeated attacks on Harris from the Republicans has been her record as the White House's so-called "immigration tzar". 

The moniker stems from the early days of Biden's presidency, when he announced Harris would be helping to coordinate relationships with Mexico and Central American countries to address the root causes of undocumented migration into the US. 

Harris defended her record on the issue, pointing to her time as the Californian attorney-general and her prosecution of human trafficking gangs.

She also wants to enact the bipartisan immigration bill that was agreed to earlier this year, before Trump effectively killed it by applying pressure to Republicans to withdraw their support. 

The bill includes funding for more border agents and to build more security fencing.

The war in Gaza similarly divides the party, with the rifts playing out even more publicly of late.

Earlier on Thursday, Harris was interrupted by pro-Palestinian protesters as she spoke at a rally in Savannah, Georgia.

During her CNN interview, Harris mostly kept the same policy as Biden, saying she's doing what she can to get the remaining hostages home and a ceasefire in Gaza.

In the interview Harris says she remains "unequivocal and unwavering in my commitment to Israel's defence". 

She repeatedly says they must get a "deal done" but offered no clear road map on how that ceasefire could be agreed to, given we are now in the 10th month of the war.

Next stop? Trump vs Harris in the debate

It seems extraordinary, but Harris has never met Trump face-to-face.

That will change in less than two weeks when they debate each other in Philadelphia. 

Harris was quizzed about how she felt when Trump had questioned her racial identity in recent months. 

She shut down the question quickly by quipping, "same old, tired playbook. Next question, please". 

But Harris did reference her Republican challenger multiple times in this interview, accusing him of mismanaging the economy while in power and working to kill the bipartisan immigration bill because it didn't serve him politically.

Trump himself was obviously watching CNN, taking to his Truth social platform to say he was looking forward to "debating Comrade Kamala Harris and exposing her for the fraud she is". 

For the past month, the Republicans have hammered Harris for not making herself available for an interview.

The CNN sit-down wasn't the authoritative performance that her team would have wanted, but it also wasn't a train wreck.

She'll have the chance to improve upon it at next month's debate.