ABC News gets rare access to VP Kamala Harris as she hits the 2024 campaign trail

As the Republican presidential candidates jockeyed for votes during the first-in-the-nation Iowa caucuses on Monday, Vice President Kamala Harris was in South Carolina, shoring up support in a state that will kick off Democrats' primary season next month.

"It's good to be back," Harris, who was making her second trip to South Carolina since the start of the new year, said before getting in her motorcade.

ABC News was granted exclusive access to the vice president during her trip, getting a rare, behind-the-scenes look as the Biden-Harris 2024 campaign kicks into high gear. ABC News Chief White House Correspondent Mary Bruce followed Harris as she traveled on Air Force Two, delivered a speech outside the South Carolina State House and met with supporters.

Harris has taken an expanded role on the campaign trail, traveling to at least 18 states over the last six months -- taking on political fights over abortion access, race and voting rights.

This, as many voters say President Joe Biden's age is a top concern. The oldest-ever sitting president, Biden would be 86 at the end of a second term. A new ABC News/Ipsos poll shows only 28% of those surveyed say Biden has the mental sharpness to serve another four years, down from about 50% in May 2020.

Bruce pressed Harris on how the campaign plans to change that perception.

"I'll tell you, the reality of it is, and I've spent a lot of time with Biden, be it in the Oval Office, in the Situation Room and other places -- he is extraordinarily smart. He has the ability to see around the corner in terms of what might be the challenges we face as a nation or globally."

Harris added: "Well, I mean, listen, you're here with me in South Carolina. You saw every room we went in. The numbers of people who are there, applauding quite loudly, and they're applauding for me and they're applauding for Joe Biden and for what we as an administration have accomplished. They're there because they believe in what we're doing and they want to see us continue to do this work."

On Monday, Harris spoke to a crowd of hundreds outside the state Capitol to mark Martin Luther King Jr. Day and laid out what she saw was at stake in the coming election.

"As vice president of the United States, I'd say, at this moment, in America, freedom is under profound threat," Harris said. "Today, in fact, we are witnessing a full-on attack on hard-fought, hard-won freedoms."

South Carolina has played a critical role in Democratic primary politics. Most voters who participate in the state's Democratic primary are Black -- the party's base. It also revived Biden's campaign in 2020 after he came in fourth in Iowa, and fifth in New Hampshire.

In a nod to South Carolina's role in Biden's 2020 win, the Democratic National Committee changed its 2024 presidential primary calendar to elevate South Carolina to be the first state to vote while demoting Iowa and New Hampshire, which national Democrats argue are not representative of their voter base or of the country, despite sharp outcry from both states.

"We're not going to wait and parachute into these communities at the last minute and ask them for their vote, we're going to earn their vote," deputy campaign manager Quentin Fulks told reporters on a call earlier this month.

"Well, that's why I'm out here," Harris told Bruce in an interview before departing Columbia. "We've done really good work, our challenge will be to let people know who brung it to them."

She added: "We have done the work that has been about bringing down unemployment, Black unemployment, to some of the lowest numbers we've ever seen … What we've done on student loan debt, we have now erased student loan debt for over three-and-a-half million people and with more to do, so we've delivered."

An area where they have not delivered, according to the ABC News/Ipsos poll, is on immigration, a critical issue for voters. Just 18% approve of Biden's handling of the border.

Biden assigned Harris the responsibility of addressing the root causes of migration at the southern border.

Democrats and Republicans are negotiating on Capitol Hill as the country faces record-shattering numbers of encounters at the southern border. Some Democrats are pressing the administration to do more, including New York Mayor Eric Adams, who has chided Washington for lacking urgency on the issue.

"Does your administration bear responsibility for that?" Bruce pressed the vice president.

"It is no secret for anyone that we have a broken immigration system, and it needs to be fixed and it would be great if we could get some bipartisan consensus to do just that," Harris resonded.

Harris has also taken a leading role when it comes to abortion rights. The California native will be embarking upon a nationwide "Reproductive Freedoms Tour" next week to highlight the administration's fight for abortion access.

While the White House has said it wants to codify the rights previously guaranteed under Roe v. Wade, without Democratic majorities in the House and Senate, its ability to act is limited.

"What can you realistically promise the American people you would do to protect these reproductive rights?” Bruce pressed.

"Well, we're gonna continue to do what we've been doing, and so that includes what we're doing through the court system, what we're doing to ensure emergency care and protection for all people in terms of access to emergency care, what we're doing to protect access to contraception is another big piece of this," Harris said.

"But here's the bottom line: From Kansas to California from, from Ohio to Virginia. When this issue has been on the ballot, the American people have voted in favor of freedoms," she added.

With a potential Biden-Trump rematch on the horizon, the Biden-Harris campaign says in the coming months voters will be presented with a stark choice involving "democracy and freedom." Harris told Bruce the campaign is gearing up for a tough fight.

"Well, I mean, we're talking about an election for president of the United States, vice president of the United States, and we have to earn that reelect. I mean, these are challenging times," she said. "I have been traveling our country, and it is clear to me that there is an intent to attack these most fundamental freedoms and liberties."

Bruce asked Harris if a rematch with former President Donald Trump, who went on to handily win the Iowa caucuses later on Monday, was a foregone conclusion.

"I don't know," Harris said. "But look, if it is Donald Trump, we've beat him before and we'll beat him again."