Longshot Democratic presidential candidate and self-help author Marianne Williamson said she is resuming her on-again, off-again campaign and called for an open Democratic National Convention in Chicago next month amid growing concerns about President Joe Biden’s age and ability to successfully take on former President Donald Trump.

Williamson, who mounted two unsuccessful bids in the 2020 and 2024 Democratic primaries, was one of the few candidates to challenge Biden for the nomination earlier this year. She did not secure a single convention delegate and garnered single-digit support in each state she was on the ballot except for South Dakota, where she received just under 12% of the primary vote -- around 2,000 votes.

“President Biden deserves our respect and our compassion and our gratitude, but the debate on Thursday night made it very clear that the Democrats need a new nominee on the ballot in November,” Williamson said in a video message she released on Tuesday. “We need to recalibrate, and we need to do so quickly. We need to have the conversation over the next two months that we should have been having over the last year and a half: a serious dialog about what's happening in this country and what it will take to beat Donald Trump.”

“Today, I throw my hat in the ring and I look forward to a meaningful campaign and an open convention in August,” she added.

Williamson initially dropped out of the race in February, but resumed her campaign shortly after and then ended it again in June. Biden secured enough delegates to win the nomination on March 12 and currently holds 3,894 delegates, followed by “uncommitted” with 35, Minnesota Rep. Dean Phillips with 4 and businessman Jason Palmer with 3. Williamson also did not receive any delegates in the crowded 2020 Democratic primary, dropping out before the first contests.

While there has been much discussion in the media and Democratic circles about replacing Biden after his widely-panned, concern-inducing debate performance last week, it has been decades since a major party in the U.S. has gone into its convention without a nominee all but chosen. Vice President Kamala Harris has been mentioned by party leaders as a natural successor and would benefit from the roughly $240 million in the Biden-Harris campaign coffers as of the end of June.

“It's imperative that this new process not be guided by media and party elites who are playing in the background, engineering, manipulating anything. This must be a genuinely democratic process,” Williamson said. “With my candidacy, I submit to the American people that a better way forward is possible and it's also necessary. I am the candidate who both foresaw the crisis in our party and had the courage to act on it.”

Democrats haven’t had an open convention since 1960, when John F. Kennedy and Lyndon B. Johnson jockeyed for votes during that year’s Democratic convention in Los Angeles.

"For months people would say about me, 'But she can't win.' I would say then, and say it again now, 'No, Biden is the one who can't win!'" Williamson wrote on social media on Tuesday. "Let me in there. I can do it."

The Associated Press contributed to this report.