Republican presidential candidate Donald Trump is set to participate in a fundraiser in late May at the home of a longtime friend. (Charlie Neibergall/AP)

An ambitious fundraising effort that aims to collect as much as $1 billion to support presumptive GOP presidential nominee Donald Trump and the Republican National Committee is taking form, with plans to kick off an aggressive schedule of finance events in Los Angeles at the end of this month.

Investor Thomas Barrack Jr., who did real estate business with Trump in the 1980s, is scheduled to host a campaign fundraiser honoring the candidate on May 25, according to multiple sources familiar with the plans. The gathering at Barrack's home is set to include a photo line, cocktails and dinner. A spokesman for Barrack declined to comment and referred questions about the event to the Trump campaign. A campaign aide confirmed the event was taking place.

The dinner fundraiser is set to be the first of as many as 50 finance events that the campaign and party are racing to set up as they try to rapidly build out a structure to appeal to major donors. Trump's willingness to participate in the functions — after months of bashing other candidates for their ties to wealthy contributors — represents a dramatic shift in his posture.

The Trump campaign, which has no apparatus to solicit contributions, is now finalizing plans with the RNC to participate in a joint fundraising committee that can accept large contributions. The so-called victory fund is expected to be led by a group of senior party financiers, including Ray Washburne, a former RNC finance chairman, according to several people familiar with the plans. Washburne left his RNC post last year to serve as finance chairman for New Jersey Gov. Chris Christie's presidential campaign. In a brief phone conversation, Washburne declined to comment.

It remains unclear who else will be part of the effort, but GOP officials are working to bring together a group of heavyweight party fundraisers with strong ties to major Republican donors in hopes of winning over reluctant contributors.

Trump faces an incredibly steep climb to raise the $1 billion that he has said is needed before November. While he has secured the backing of some prominent donors and fundraisers, including New York investor Anthony Scaramucci, many top GOP bundlers have been privately discussing their reservations about helping the real estate magnate raise funds. The angst is so acute that some have offered to quietly send over a list of the donors they know, but do not even want to be assigned a bundler number to get credit for the checks they bring in.

One exception is Barrack, a prominent real estate investor, founder and executive chairman of Colony Capital and a longtime Trump friend. He is not new to politics, having served as a deputy undersecretary at the Interior Department in President Ronald Reagan’s administration.

In February, Barrack endorsed Trump, showering praise on his friend. “His mastery of financial, political and economic intellectual complexity combined with his charm and emotional intelligence when partnering with New York labor unions, governmental regulatory bodies, Wall Street lenders, sophisticated institutional global investors, demanding developers, global media and entertainment companies and hard-working employees, is a dynastic art form,” Barrack said in a statement issued by the Trump campaign.

Barrack's event is expected to kick off a series of fundraisers for the campaign and the still-forming joint fundraising committee. Such a fund is one of the most lucrative ways for a presidential candidate to scoop up big donations for the fall general election battle. That’s because a victory fund can take contributions many magnitudes greater than the $2,700 an individual can give to a candidate’s campaign per election. The additional funds are routed into party coffers, which then use the money to finance national get-out-the-vote operations.

In 2012, GOP presidential nominee Mitt Romney raised nearly $500 million through a joint fundraising agreement with the three national Republican party committees and four state parties, an effort that began in early April 2012. Because of all the committees involved, an individual donor could give nearly $135,000. By the end of June 2012, Romney Victory had already scooped up $140 million.

Now, such joint fundraising efforts can solicit even larger amounts, thanks to the Supreme Court’s 2014 decision in McCutcheon v. Federal Election Commission. That did away with an aggregate cap on how much individual donors can give to federal campaigns, parties and PACs in one year. In addition, a measure tucked into a 2014 appropriations bill allowed national parties to collect separate checks for convention, legal and building expenses.

Democratic front-runner Hillary Clinton has pursued this strategy most aggressively. In the fall, she set up a victory fund with the Democratic National Committee and a record 32 state committees that can accept up to $356,100 per donor per year.