Marianne Williamson on presidential campaign, new DNC primary schedule: 'This Week' exclusive

Self-help author and Democratic presidential candidate Marianne Williamson told ABC News’ Chief Washington Correspondent Jonathan Karl that she doesn’t see her long-shot bid for the White House as a challenge to President Joe Biden -- but as “challenging a system.”

During an exclusive, wide-ranging interview for ABC’s “This Week" on Sunday, Williamson discussed why she’s seeking the Democratic Party’s nomination in 2024, despite an unsuccessful bid for the White House in 2020 and an unsuccessful congressional campaign in 2014.

“I want to be president because this country needs to make an economic U-turn,” Williamson told Karl, describing herself as an "FDR Democrat" and describing a future in which voters "have to rise up."

Among the priorities she named were free health care, free college and free child care as well as "fundamental economic reform."

“The system that effectuates and perpetuates that kind of income and opportunity inequality is not changing itself. ... It’s not going to change if we continue to elect the same-old, same-old," she said.

Williamson officially announced her presidential campaign Saturday afternoon, at Washington's Union Station. She’s currently the only Democratic challenge to President Biden, should he run for reelection as expected.

A bestselling writer and popular speaker, Williamson built a national profile in part through her appearances on Oprah Winfrey's daytime talk show. She has stirred controversy for some of her past comments about depression and criticizing vaccine mandates while supporting vaccinations themselves.

“I think it was the Associated Press [that] said you are the longest of long shots. ... Why do you think you can do this?” Karl asked.

“I would bet that the Associated Press also said that Hillary Clinton was a shoo-in [in 2016],” Williamson said.

“I don't know if they would've used that language, actually,” Karl pushed back.

“Maybe not. ... So the system that is now saying that I'm unserious, I'm not credible, or I'm a long shot is the very system that protects and maintains this idea that only those whose careers have been entrenched within the system that drove us into a ditch should possibly be considered qualified to lead us out of that ditch,” Williamson said.

“My qualification is not that I know how to perpetuate that system. My qualification is that I know how to disrupt it. And that is what we need," she said.

Williamson suggested that as president, she would seek to “cancel all college loan debt,” before criticizing Biden for not doing more without Congress -- such as criminally declassifying marijuana.

Karl followed up, pointing to the checks on a president's power, such as judicial review and the legislature, which Williamson brushed aside.

"There are many things that the president can do without working through Congress," she said, adding, "He also could demand that there be an audit of every single cent that is being spent by the Pentagon. [He] could also cancel all of the contracts with union-busting companies."

On foreign policy, Williamson said she agreed with the White House's current approach in Ukraine while repeating her past criticisms of U.S. military operations abroad, such as the wars in Iraq and Vietnam.

Regarding China, Williamson seemed to draw a line at vowing a military response if Beijing were to attack the self-governing island of Taiwan but said China could not be a "bully."

"We must make a stand for such things as human rights. At this point, we must be committed that this not spill over into a military confrontation," she said.

Though Biden has not yet jumped into the race, most major Democrats expect him to make an announcement in the coming months and he has repeatedly said he intends to run again.

“But there’s too many other things we have to finish in the near term before I start a campaign,” he told ABC News anchor David Muir last month.

At 80 years old, Biden is the oldest serving president in U.S. history and questions about his age have swirled as other candidates have launched bids for 2024. When asked if the president's age is an issue, Williamson told Karl “I’m not going there. I don’t think ageism has any place in our thinking.”

She would not directly answer if she would support Biden, should he win the party’s nomination. (In the 2020 primary, she backed Vermont Sen. Bernie Sanders after withdrawing.)

“Will you endorse him [Biden] if he wins the nomination?” Karl asked.

“I will certainly endorse the candidate who I feel can beat the Republicans, absolutely,” Williamson said.

“But if he's the Democratic nominee, will you endorse him?” Karl pressed.

“I will do whatever I feel I can do as an American to make sure that the neo-fascist threat that is represented by some aspects of the Republican Party does not win in 2024,” Williamson said.

And though she called Biden "a nice man" with a "good heart," she also would not rule out running as a third-party candidate in the general election if she loses the primary.

“I’m not saying that I would run as a third-party candidate,” she initially said, but when asked if she definitely wouldn’t, she only replied that she would do what she can “to make sure that the overriding issue is addressed.”

Asked later if she thought former President Donald Trump could defeat Biden in the general election, she said, "I would do everything I could to make sure that didn't happen."

Last month, the Democratic National Committee voted to change the 2024 primary calendar, removing New Hampshire from its slot as the first primary and moving South Carolina forward, with supporters of the change saying it allowed more diverse voters early influence.

Williamson has said that she’ll participate in the New Hampshire primary, despite it likely falling out of compliance. She also plans to make several stops in the state from March 8-13.

“The DNC should not be rigging this system,” Williamson said.

“So that’s what’s going on, is they’re rigging the system for Biden?” Karl asked.

“They even admit that. They know that the president did not do well in New Hampshire,” Williamson said. “They know that New Hampshirites are very open to independent and more progressive voices. And they know that he did very well in South Carolina. They're not even-- you know this, I know this, they know this. And they're not even pretending otherwise.”

The party's national committee will not hold debates with challengers to the president, but Williamson thinks they should.

“Do you expect that Biden will debate you?” Karl asked.

“He certainly should debate me,” Williamson said. “It's called democracy. And I'm running as well.”

Williamson qualified for two Democratic debates in the last presidential cycle, where she made a splash for her closing argument, addressing then-President Trump directly and saying, “I'm going to harness love for political purposes. I will meet you on that field. And, sir, love will win.”

Karl asked Williamson about media coverage of her in 2020, noting she was previously labeled as “anti-science, anti-vax [and] a crystal lady” and asking how Democrats should view her candidacy this time around.

“Well, I am a Democrat," she said. “I'm old enough to remember a time when the Democratic Party more than not, did make an unequivocal stance. ... [T]he Democratic Party needs to be a conduit for the healing of this country," she continued. "But first, the Democratic Party needs to look in the mirror and heal itself.”

You can read the full transcript of the interview here.