(Bloomberg) —Just two days after locking up the Republican presidential nomination, Donald Trump is moving quickly to build a fundraising operation capable of reeling in hundreds of millions of dollars he’ll need to win the White House.

Heading up the operation as national finance chairman will be Steven Mnuchin, a business associate of Trump’s and also chairman and CEO of Dune Capital Management LP, the campaign announced on Thursday.

“Steven is a professional at the highest level with an extensive and very successful financial background,” Trump said in a statement. “He brings unprecedented experience and expertise to a fundraising operation that will benefit the Republican Party and ultimately defeat Hillary Clinton.”

The campaign will sign a joint fundraising agreement with the Republican National Committee “in the very near future,” said Mnuchin, who expects to raise more than $1 billion between Trump’s campaign and the party. Trump, who’s made much of the fact that he’s self-funded a big portion of his campaign, will continue making contributions, Mnuchin said.

The campaign “will work closely with the party,” he said.

Deep TiesMnuchin, a registered Republican, said he joined the presumptive Republican nominee at Trump Tower on April 19, the night he won the New York primary. The next day, Trump asked him to join the campaign. They also had dinner in Los Angeles before Trump began his campaign, he said.

“He’s bringing a lot of people into the party who have not been part of the party in the past,” Mnuchin said. “Donald’s appeal is way beyond the traditional political candidates, and what he stands for and represents is a completely new approach.”

The two men have known each other for 15 years and have done business together, Mnuchin said, declining to comment further on the nature of their dealings. Trump sued lenders including Dune Capital in 2008 seeking to extend the term of a construction loan for Trump’s 92-story luxury hotel and condominium tower in downtown Chicago. In March 2009, Trump and the lenders agreed to suspend legal action between them.

Mnuchin said he particularly likes Trump’s economic platform, including a plan for simplifying the tax code, and expects the real estate developer to surround himself with smart people.

Mnuchin is part of a group of businesspeople Trump has excoriated. In August, Trump said hedge fund managers were “getting away with murder” as he touted his proposal to end the so-called carried interest loophole, which gives private equity and hedge fund managers preferential tax treatment.

“The hedge fund guys didn’t build this country,” Trump said at the time on CBS’ Face the Nation. “These are guys that shift paper around and they get lucky,” he said. “They are energetic. They are very smart. But a lot of them—they are paper-pushers. They make a fortune. They pay no tax. It’s ridiculous.”

Mnuchin declined to comment on Trump’s attacks on the carried-interest tax loophole that many hedge fund managers use to lower their taxes. But he said he’s already gotten calls from fellow hedge fund managers and others on Wall Street expressing their support, he said.

Business and PoliticsLike Trump, Mnuchin has given money to Democrats, including about $7,000 to Hillary Clinton for her U.S. Senate bids and her previous presidential campaign. He has also given a substantial amount to Republicans, including $20,000 to the Republican National Committee. But the Democratic donations outweighed the ones to Republicans, according to records on opensecrets.org.

In 2003, the new finance director started a hedge fund with $1 billion from George Soros, the liberal New York financier who has spent more than $13 million to support Hillary Clinton and other Democrats this election cycle.

Mnuchin spent 17 years at Goldman Sachs Group Inc., working his way up to partner and becoming head of the mortgage department before joining Hank Paulson in the executive suite, becoming the firm’s chief information officer in 1999.

At Dune, he purchased the remains of IndyMac Bank, the Pasadena, California-based mortgage lender that collapsed in 2008. Notoriously press-shy, the executive endured 2011 protests on the lawn of his Bel Air mansion by foreclosed homeowners angered at his lender’s handling of soured mortgages.

Mnuchin cashed in on the firm’s initial public offering and then left Goldman in 2002 to join Lampert’s ESL Investments hedge fund as vice chairman. A year later he started the fund with Soros’s money. And in 2004, with two other ex-Goldman Sachs partners, he formed hedge fund Dune Capital Management, which led a group that raised $1.55 billion to acquire IndyMac from the FDIC in 2009.

Starting his career in the early 1980s as a trainee at Salomon Brothers before moving to Goldman Sachs in 1985, Mnuchin was front and center for the advent of instruments like collateralized debt obligations and credit default swaps. He has called securitization “an extremely positive development in terms of being able to finance different parts of the economy and different businesses efficiently.” The pitfalls of the financing method came later, he’s said.

Mnuchin’s father, Robert Mnuchin, was a partner at Goldman Sachs in the 1960s. The second-youngest of five siblings, Steven attended the prestigious Riverdale Country School and then Yale University, where his roommate was Edward Lampert, who would go on to become a hedge-fund manager and owner of Sears.

—With assistance from Sahil Kapur.

o contact the authors of this story: Jennifer Jacobs in Washington at jjacobs68@bloomberg.net Dakin Campbell in New York at dcampbell27@bloomberg.net To contact the editors responsible for this story: Mike Nizza at mnizza3@bloomberg.net Elizabeth Titus at etitus2@bloomberg.net