Billionaire donors are defecting from Trump. Here's who to watch.

Former President Donald Trump, who launched his 2024 campaign on Tuesday, is already facing defections among the billionaire megadonors behind his previous campaigns.

Ken Griffin, the founder and CEO of hedge fund Citadel, on Tuesday threw his support behind a potential run from Florida Gov. Ron DeSantis, while criticizing Trump as a "three-time loser" in an interview at the Bloomberg New Economy Forum in Singapore.

A more significant blow came on Wednesday from Stephen Schwarzman — chairman, CEO and co-founder of private-equity giant Blackstone — who gave millions to Trump's 2020 campaign and various pro-Trump groups but vowed to reserve his support in the upcoming Republican primary for someone among "a new generation of leaders," Axios reported.

As election officials tally the final votes in a disappointing midterm election for Republicans, Trump faces scrutiny over the poor performance of Congressional candidates who received his endorsement. In a vulnerable moment for Trump, further donor defections could hamper his presidential run barely after it has started.

Here are wealthy Trump allies to keep an eye on as others defect:

Miriam Adelson

Miriam Adelson, wife of deceased casino magnate and top Republican donor Sheldon Adelson, could play a pivotal role in the Republican presidential primary.

Previously, the Adelsons drew on their immense riches in support of Trump. Ahead of the 2020 election, the couple gave $90 million to a pro-Trump super PAC called Preserve America. In her own right, Miriam Adelson donated about $800,000 combined to Trump Victory -- the Trump campaign and the Republican Party's joint fundraising vehicle -- and an additional $5 million to America First Action, another Trump-aligned super PAC, for both of his presidential runs, campaign filings show.

In 2018, Trump awarded Miriam Adelson with the Medal of Freedom.

Since Sheldon Adelson died in January 2021, however, Miriam Adelson's political giving has relatively slowed down and the exact direction of her contributions remains uncertain. Ahead of the recent midterms, she gave $10 million to a Super PAC aligned with Senate Minority Leader Mitch McConnell, a frequent target of Trump's derision.

Adelson, whose net worth is estimated by Forbes at nearly $30 billion, plans to remain neutral in the 2024 primary, Politico reported last month. Regardless, candidates will likely continue to seek her backing.

Richard Uihlein

Billionaire shipping magnate Richard Uihlein has emerged as a foremost Republican donor as the presidential primary campaign nears.

As of June, Uihlein – CEO of the shipping and packaging company Uline – gave more than any other individual Republican donor to candidates running in the midterm elections, campaign disclosure reports show.

In recent years, a large share of Uihlein's contributions have gone to Trump and Trump-related causes. In combined giving over the course of the 2016 and 2020 races, Uihlein gave nearly $900,000 to Trump Victory as well as $750,000 to Trump-aligned super PAC America First Action, campaign filings show.

During the 2022 midterms, Uihlein was among the few top GOP donors that backed Trump-aligned candidates that have questioned the results of the 2020 election.

Meanwhile, Uihlein has given tens of millions over recent years to a prominent conservative group called Club for Growth, which once supported Trump and several candidates he endorsed in 2022 but has in recent months distanced itself from the former president.

Club for Growth appeared to fuel misgivings about Trump on Monday, when the group released polling data showing DeSantis leading Trump in head-to-head surveys across early primary states Iowa and New Hampshire.

Larry Ellison

Larry Ellison, chairman of database management company Oracle and eighth-richest person in the world, according to Forbes, hosted a fundraiser for Trump's 2020 re-election bid and has backed a host of rightwing causes, including the Federalist Society.

In March, Ellison gave $1 million to the Tennessee Conservatives PAC, which one month later funded a lawsuit fighting a residency requirement that was used to throw a Trump-backed candidate off the primary ballot.

Despite the previous support for Trump, Ellison has recently put his financial backing behind a different potential 2024 contender. Ellison has donated $25 million over the past couple of years to a longstanding Super PAC aligned with Sen. Tim Scott, R-S.C., a potential candidate often mentioned among a set of viable Trump challengers.

Peter Thiel

Peter Thiel, a venture capitalist and chairman of the software company Palantir, contributed a total of $500,000 in support of Trump's 2016 and 2020 campaigns.

A year before the 2020 election, Thiel arranged a private meeting between Trump and Mark Zuckerberg, the CEO of Facebook-parent Meta, NBC News reported. In February, Thiel left the board of directors at Meta in order to focus on providing financial support for Republican political candidates.

Thiel threw tens of millions behind two Trump-aligned Senate candidates in the midterms: J.D. Vance in Ohio and Blake Masters in Arizona. Vance is projected to win his race; Masters is projected to lose.

Thiel's spending in the midterms was hardly exclusive to close Trump allies, however. Thiel gave nearly $50,000 to a joint fundraising committee affiliated with Republican House Speaker Kevin McCarthy and $10,800 to a Super PAC aligned with Sen. Ted Cruz, R-Texas. Observers widely expect Cruz, who ran against Trump in 2016, to consider another White House run.