By Jeff Mason

WASHINGTON (Reuters) - President Joe Biden will get a boost from Democratic predecessors Barack Obama and Bill Clinton on Thursday at a fundraiser in New York slated to raise more than $25 million and add some oomph to Biden's 2024 re-election campaign.

Biden and the two former commanders-in-chief will take part in a discussion moderated by "The Late Show" host Stephen Colbert at Radio City Music Hall in front of thousands of guests at what Biden's re-election campaign said would be the most successful political fundraiser in history.

Musicians Queen Latifah, Lizzo, Ben Platt, Cynthia Erivo and Lea Michele are slated to perform, and some high-paying attendees will get their pictures with the three presidents taken by star photographer Annie Leibovitz.

Biden, 81, has faced concerns about his age and fitness for a second four-year term. Recent Reuters/Ipsos polls show his approval rating at 40% and a tight race with Republican challenger Donald Trump, who is 77, ahead of the election on Nov. 5.

Tickets for Thursday's event are between $250 and $500,000, according to a Democrat familiar with the event. More than 5,000 people were expected to attend. The event will not be televised, but the campaign plans to post content from it on social media. Small-dollar donors can pay $25 to take part in a virtual event with the three men.

Biden has visited all of the top battleground states since a fiery State of the Union address earlier this month, but mostly has spoken to much smaller crowds, part of a deliberate strategy to emphasize interactions with ordinary Americans. Vice President Kamala Harris has crisscrossed the country as well.

The show of support from Obama, who is still enormously popular with Democrats, could bolster enthusiasm from some young voters and other progressives who voted for Biden in 2020 but are furious about his staunch backing of Israel in its response to the Oct. 7 Hamas attacks.

"The numbers don’t lie: today’s event is a massive show of force and a true reflection of the momentum to reelect the Biden-Harris ticket,” campaign co-chair Jeffrey Katzenberg said in a statement.

Biden's re-election effort raised more than $53 million in February and $10 million in the 24 hours following his March 7 address to Congress. Biden has been routinely outraising Trump.

Obama has voiced concerns to Biden that Trump could win, ahead of a shakeup of Biden's team that sent two top White House aides to the Wilmington, Delaware-based campaign.

The former president spent time at the White House recently putting together a video highlighting the anniversary of his signature Affordable Care Act, also known as Obamacare. Biden is campaigning hard on his efforts to strengthen the law and accuses Republicans of seeking to end it.

Trump used Biden's event with Obama and Clinton to appeal to his own supporters as well. "The Obama-Clinton cartel thinks they will beat us tomorrow, but I have something they'll NEVER have," he said in a fundraising appeal on Wednesday, referring to his supporters.

(Reporting by Jeff Mason; Editing by Heather Timmons and Leslie Adler)

Obama, Bill Clinton to join Biden to raise $25 million at event with Queen Latifah and Lizzo