A longtime Democratic figure and former presidential candidate stepped back onto the public political stage Thursday when it was announced he will be serving as campaign manager for Robert F. Kennedy Jr.'s effort to beat out President Biden for the party's 2024 nomination.

Dennis Kucinich, a former Ohio Congressman who unsuccessfully ran for the 2008 Democratic presidential nomination against then Sens. Hillary Clinton and Barack Obama, has been advising Kennedy for months, and introduced him at his campaign kickoff in Boston last month.

Kennedy's campaign made the appointment official in a press release touting Kucinich's experience and referred to him as "one of the foremost progressive voices in American politics."

RFK JR. SAYS DEMS HAVE BECOME ‘PARTY OF WAR,’ AMERICANS CAN'T AFFORD A $1,000 EMERGENCY

Dennis Kucinich and Robert F. Kennedy, Jr.

Former Democratic Ohio Congressman and presidential candidate Dennis Kucinich (left) and Democratic presidential candidate Robert F. Kennedy, Jr. (right). (Getty Images)

"Dennis Kucinich has brought invaluable electoral experience to our campaign," Kennedy said in a statement. "He knows how the system works from the inside out, and his deep knowledge of issues and his personal integrity are fully aligned with the core values our campaign is bringing to American politics."

Since launching his campaign last month, Kennedy has gained a sizable chunk of support from Democrats opting not to support Biden for re-election. According to a Fox News poll released April 27, 19% of Democratic primary voters said they would support Kennedy, while 9% said they would support author Marianne Williamson.

The support for Kennedy and Williamson made up more than a quarter of Democratic primary voters participating in the poll. It found, however, that Biden still had support from 62% of the party.

ABC NEWS ADMITS EDITING RFK JR'S VAX CLAIMS

Marianne Williamson in New Hampshire

Democratic presidential candidate Marianne Williamson campaigns in Portsmouth, New Hampshire on March 9, 2023. (Marianne Williamson campaign )

Kennedy and Williamson have decried the Democratic National Committee's (DNC) plan not to hold any primary debates between the three candidates, although it is common for the party in power to avoid primary elections when in control of the White House.

Both Williamson and Kennedy have also made New Hampshire a key target of their race since the DNC changed the order of primaries. The national party bumped New Hampshire from the lead-off primary spot, but the state will likely hold an unsanctioned primary on its preferred date – meaning Biden may not even appear on the primary ballot in that contest.

President Biden

President Joe Biden speaks about the economy at the International Union of Operating Engineers Local 77 facility in Accokeek, Maryland, on April 19, 2023. (Jim Watson/AFP via Getty Images)

CLICK HERE TO GET THE FOX NEWS APP

Fox News' Paul Steinhauser and Houston Keene contributed to this report.