President Biden is headed to a fundraiser Saturday featuring actor George Clooney, actress Julia Roberts, and a late-night host, Jimmy Kimmel, as most of Hollywood throws its support behind his re-election bid.

Mr. Clooney and Ms. Roberts, both Academy Award winners, are only the latest stars from Hollywood’s highest tier to throw in with the Biden campaign. In May, a two-time Oscar winner, Robert De Niro, held a press conference for the campaign outside President Trump’s recent criminal trial at Manhattan, where the actor predicted that Trump would “destroy the whole world” if re-elected.

A fiercely anti-Trump comedian, Mr. Kimmel has been a subject of Trump’s ire online, with Trump posting about Mr. Kimmel earlier this year saying, “Has there EVER been a WORSE HOST than Jimmy Kimmel at The Oscars.”

“Get rid of Kimmel and perhaps replace him with another washed up, but cheap, ABC ‘talent,’ George Slopanopoulous,” Trump said. “Also a really bad politically correct show tonight, and for years — Disjointed, boring, and very unfair.”

 During the ceremony, Mr. Kimmel read out to the audience Trump’s negative feedback, and then asked, “isn’t it past your jail time?”

Earlier this spring, Mr. Biden held a fundraiser featuring Presidents Obama and Clinton, as well as stars such as Lizzo, Lea Michele, and Queen Latifah.

The fundraiser also represents an effort from the Biden campaign to match the fundraising levels claimed by Trump’s campaign in the wake of his guilty verdict.

In the days after Trump was convicted, his campaign claims to have raised some $141 million, though these fundraising levels have not been confirmed in Federal Elections Commission filings and won’t be until later this month.

The latest FEC filings show that Trump outraised Mr. Biden in April, $76 million to $51 million, though Mr. Biden’s campaign still maintains an overall cash advantage.

The overwhelming majority of Hollywood’s stars and power brokers have backed Mr. Biden, while Trump has garnered the endorsements of a handful of conservative celebrities, like musician Kid Rock, actor John Voigt, and a country music singer, Jason Aldean.

 Some higher-wattage celebrities have publicly telegraphed that they won’t be supporting Mr. Biden’s re-election. A number of these celebrities appear to have pulled their endorsements due to conservative turns in their politics, like actor Dwayne “the Rock” Johnson, one of Hollywood’s biggest box office performers, who told “Fox and Friends” that his 2020 endorsement of Mr. Biden caused “division” in his circles. He has previously complained about “cancel culture, woke culture, division, etcetera.”

Other celebrities have publicly refused to endorse Mr. Biden over objections to his policy concerning Israel and Hamas, like outspoken musician Cardi B, who endorsed Mr. Biden in 2020 but said she wouldn’t do so in 2024. She says America shouldn’t pay “for endless wars for countries that have been going through s— for a very long time.”

Mr. Clooney has had his own issues with White House policy, complaining by text message last week about the president’s denunciation of the International Criminal Court’s issuance of arrest warrants for Israeli leaders, according to the Washington Post.

Mr. Clooney’s wife, Amal Clooney, is a human rights lawyer who served as one of six experts on an ICC panel that reviewed the evidence ahead of issuing the warrants, which allege that the Israeli military has committed war crimes. Mr. Biden called the warrants “outrageous,” and the administration has signaled openness to sanctioning the ICC, which could affect Ms. Clooney.

Attorney Robert Kennedy Jr., who is running for office as an independent, has also received some celebrity endorsements, including from comedian Rob Schneider, actress Alicia Silverstone, and actor Kevin Spacey.

“When the world turned its back on me, Bobby leaned in,” Mr. Spacey said in his endorsement of Mr. Kennedy. The actor fell out of the public’s favor in the late 2010s after allegations from the early 1990s surfaced. However, investigations into the allegations at Los Angeles did not result in charges, and the case against Mr. Spacey at Nantucket was dropped. He was also acquitted in a trial in the United Kingdom in 2023.

While celebrity endorsements often make headlines, it’s not clear how much impact they have on Americans’ decisions in the voting booth. A survey by the Hill and HarrisX found that the majority of respondents, 65 percent, say celebrity endorsements have no effect on their voting decisions, while 11 percent said that endorsements make them more likely to vote a certain way.

Another 24 percent said that a celebrity endorsement made them less likely to vote for a candidate. Among Republicans, that number was 38 percent. One area where celebrity endorsements do matter significantly is fundraising, as their presence at high-wattage events can attract deep-pocketed donors.