When Robert De Niro showed up outside a Manhattan courthouse to decry Donald Trump as his New York hush money trial was winding down, it sparked a life-imitates-art screaming match with a nearby group of the former president's supporters.

“You are gangsters!” De Niro, who starred in “Goodfellas” and won an Oscar for “The Godfather Part II," shouted at the Trump backers, who responded with obscenities.

There are plenty more Hollywood storylines still to come in the 2024 campaign: Celebrities are increasingly lending their star power to President Joe Biden, hoping to energize their fans to vote for him in November and to entice donors to pony up for his reelection effort.

On Saturday, A-listers George Clooney and Julia Roberts will team up with former President Barack Obama at a Biden fundraiser in Los Angeles, where the three will be interviewed by late-night talk show host Jimmy Kimmel. Roberts and Kimmel have already begun soliciting donations via text for Biden, who is skipping a weekend peace conference on Ukraine being held in Switzerland to attend the event.

Director Steven Spielberg is involved in storytelling efforts for the Democratic National Convention in August. Lenny Kravitz, Barbra Streisand and James Taylor have all performed for Biden donors.

Others who've sent fundraising emails, organized events or otherwise lent their support include Connie Britton of “The White Lotus” fame, singer-songwriter Carole King, “Bridgerton” creator Shonda Rhimes, singer Christina Aguilera, “The Equalizer” actress Queen Latifah and “Star Wars” actor Mark Hamill, who turned up in the White House briefing room last month to personally praise the president.

And, in another instance blurring lines between real life and make-believe, during a fundraiser at the home of veteran actor Michael Douglas, Biden, the actual president, congratulated the star of the 1996 hit “The American President” on his fictional administration's success.

Ballot box star power?

For all the celebrity supporters, though, there's little expectation they can determine votes. Rather, they are seen as having the ability to inject excitement that helps energize supporters.

Lexi Underwood, whose credits include the streaming series “Little Fires Everywhere,” calls acting a “contact sport” that allows her to interact with the public and makes her determined to use her influence responsibly. She has participated in a recent virtual ”Students for Biden” event and traveled to Nevada to appear at campaign events focused on women's health issues.

“I’m very fortunate to have certain eyes on me," said Underwood, 20. "I feel really responsible to make sure that what I put out there, either people are being informed on things that they weren’t previously informed on, or that I’m motivating them to get out there and vote.”

Biden's campaign says its chief focus is finding authentic and trusted messengers who can promote the president's policy achievements and raise the alarm about GOP “extremism," and that means deploying everyday supporters as well as famous ones. It has produced ads featuring a Pennsylvania union worker, a Black entrepreneur in Detroit and women adversely affected by strict abortion limits in Texas.

Fai Nelson, a human resources worker who attended a recent Vice President Kamala Harris event in Prince George's County, Maryland, said celebrity voices can make a difference “if they can touch the audience.”

“It’s whether the message is relevant," said Nelson, 42.

Lessons from last time

During the pandemic-era campaign of 2020, Biden's campaign featured celebrities in scores of virtual events that showed the importance of staying flexible so that stars can present themselves in the most authentic ways.

Adrienne Elrod, who served as Biden’s 2020 director of surrogate strategy and operations, said famous Biden supporters often “will come forward with their own ideas” on how to help the campaign and what issues they'd like to focus on.

“We’ll oftentimes have ideas for them as well," she said. “That’s why there’s always a very productive working relationship when we’re engaging these folks.”

De Niro has taken on an increasingly prominent role in Biden's campaign. Before his confrontation with the Trump supporters, the actor held a press conference calling the former president a “clown." He's also attended Biden fundraisers and narrated a campaign ad accusing Trump of having “snapped” after he lost the 2020 election.

Karoline Leavitt, a spokesperson for the former president's campaign, said, “The only people in America who support Joe Biden’s failing campaign are elitist Hollywood celebrities," adding that Trump “speaks for the forgotten men and women of this country.”

Trump has his own list of celebrity endorsers, which includes musicians Kid Rock and Ted Nugent, UFC CEO Dana White, media personality Caitlyn Jenner and actors Dennis Quaid and Jon Voight, as well as comedian Roseanne Barr.

Elrod said other stars are anxious to follow De Niro's lead for Biden but are waiting "until the moment can truly be maximized" before they get involved. She pointed to 2020, when Bruce Springsteen narrated a Biden ad featuring his song “My Hometown” just before the election.

"I think you’ll see more moments like this, when we’re using those voices strategically and effectively at the time that makes the most sense for us on the campaign,” said Elrod, who is a Biden campaign spokesperson this cycle.

David Schmid, an English professor at the University of Buffalo who studies popular culture, said celebrities can influence fans' aspirations and what they consume. But their influence “over peoples’ voting habits has been really exaggerated," he said.

That's the case for Alex Dillion, a rising sophomore at American University in Washington who also attended the Harris event in Maryland. Asked which famous person might influence him politically, Dillion offered, “Maybe Obama.”

Schmid said one celebrity with outsized political influence might be Taylor Swift, who sent shockwaves even through the NFL last season. She endorsed Biden in 2020 and is being openly courted by the campaign this time on social media, and even in a press release that saluted her latest album.

Her touch isn't a guarantee of victory, though. In 2018, Swift endorsed two Democratic candidates in Tennessee who lost. And Schmid said that even someone as famous as Swift “knows things are polarizing and they don't want to take major risks” on candidates and contentious issues.

For all the Biden team's work with celebrities, the president still tries to cultivate the image of someone in tune with ordinary people.

During a campaign swing through Saginaw, Michigan, the president visited a public golf course and met with community activist Coleman Hurley III and his son.

“The celebrities that have everything they want and they need, they may possibly be out of touch," the older Hurley said later in a phone interview.

As for ordinary Americans, Hurley added, Biden needs to be able to "relate and see where they live ... and then have a conversation about some of the different struggles or issues that we, or other Americans, face.”

FILE - Lenny Kravitz arrives at MusiCares Person of the Year, Feb. 2, 2024, in Los Angeles. Celebrities including Kravitz are increasingly lending their star power to President Joe Biden, hoping to energize fans to vote for him in November or entice donors to open their checkbooks for his reelection campaign. (Photo by Jordan Strauss/Invision/AP, File)

Hollywood's A-listers are lining up behind Joe Biden. Will their support matter in November?