Hours after delivering his final speech to a cheering crowd at the Democratic National Convention in Chicago, President Biden was relaxing in a tranquil, sunny vineyard in California, thousands of miles away.

First Lady Biden and some of his children and grandchildren are spending the week at an 8,000-acre estate owned by Democratic megadonor Joe Kiani. The president is due to leave for Delaware on Sunday.

The elegant mansion, nestled on a back road in the tan hills of Santa Barbara County, is one of a string of luxury homes owned by wealthy Democratic donors that have hosted the Biden family in recent years.

Biden has close ties to Kiani, the billionaire founder and CEO of Irvine medical technology company Masimo. The president has called the entrepreneur and Democratic megadonor “one of my closest friends.” Kiani sits on a council that advises the president on science and technology.

The relationship has infuriated Republicans, who have raised ethical concerns about Biden vacationing at the home of a major Democratic donor.

Elected officials, including the president, are generally required to disclose gifts under ethics laws enacted after the Watergate scandal, but public officials do not have to disclose “meals, lodgings, or entertainment received as personal entertainment.”

Richard Painter, a professor of corporate law at the University of Minnesota, said Biden would have to disclose his “free use” of friends' homes, but wouldn't have to report them if the friends were living with him.

“It's common for presidents to stay over at friends' houses and so on,” said Painter, who served as the White House's chief ethics counsel under George W. Bush, “but if it's free use of the house, and President Biden has done that several times, that needs to be in the report.”

It's unclear whether Kiani was at the mansion during Biden's vacation, and a spokesman for Kiani did not return calls about Biden's stay.

Biden isn't the only president to enjoy hospitality from political donors and supporters. President Barack Obama and his wife, Michelle Obama, vacationed at a Martha's Vineyard estate owned by Chicago financier David Schulte. Martha's Vineyard was also a popular getaway for President Clinton. Sunnylands, the Rancho Mirage estate owned by Walter and Leonore Annenberg, was a presidential destination for decades.

Kiani's home is located in the foothills of the San Rafael Mountains, about an hour north of Santa Barbara. The property is set back a few miles from the highway and accessed via a two-lane road surrounded by horse pastures, white fences, and gnarled oak trees.

The area has attracted the famous, the wealthy and the deeply private for decades: Kiani Ranch is near Michael Jackson's former estate, Neverland Ranch, now owned by billionaire Democratic donor Ron Burkle, and President Reagan's Rancho del Cielo ranch, about 15 miles away.

The rhythm of life in Santa Barbara County wine country has remained largely unchanged this week, residents say, except for a flurry of excitement after a Secret Service agent was seen buying a sandwich at Los Olivos Grocery, a local gourmet market and deli in Santa Ynez.

“He and I don't really see eye to eye outside of this place,” said Andrew Wilson, a resident who didn't vote for Biden in 2020. But, waving toward the golden hills, “I can't blame him for wanting to be here.”

Biden and his family have a tradition of spending the holidays at the homes of Democratic donors: The president and his family spent three consecutive Thanksgivings at private equity billionaire David Rubenstein's Nantucket estate and rang in the 2023 New Year at the U.S. Virgin Islands home of Democratic donors Bill and Connie Neville.

In 2022, Biden and first lady Jill Biden spent a summer week at a seaside mansion in South Carolina owned by Democratic donor Maria Alwyn. Last summer, the Bidens vacationed at billionaire Tom Steyer's home on the shores of Lake Tahoe.

Republicans are also taking notice. Earlier this year, the conservative think tank Center for American Renewal wrote: asked the Department of Justice. They called for an investigation into Biden's vacations for failing to disclose them as gifts from donors.

“There are gaffes here and there right now,” Painter said. “I wouldn't put Biden in the bad category. He's had one or two gaffes that should have been reported.”

Kiani's appointment to the President's Council of Advisors on Science and Technology in 2021 also angered rivals. Republicans on the House Oversight Committee have called for an investigation into that appointment and another appointment of a major Democratic donor.

An April 2022 letter signed by 12 House Republicans said Kiani's company has won nearly $3 million in federal contracts from three government agencies since Biden took office in January 2021. The company had also won contracts in previous administrations, but Kiani's close ties to Biden “create the impression that he has benefited from political contributions,” the lawmakers wrote.

Kiani has been a staunch Democratic donor for more than two decades, according to election records, and during Biden's 2020 presidential run, he raised $1.3 million for his campaign, according to federal filings.

The billionaire also gave $1 million to Unite the Country, a super PAC that supports Biden. Other donations to Democratic organizations include $500,000 to the progressive super PAC Priorities USA, $250,000 to Rep. Nancy Pelosi's Victory Fund and about $400,000 to an organization that works to elect Democrats to the House of Representatives.

Kiani's involvement in politics goes beyond campaign donations.

In 2013, he founded the Patient Safety Movement Foundation, a nonprofit organization dedicated to reducing preventable patient deaths in U.S. hospitals. Healthcare has become a key political focus. Kiannia has testified before Congress and spoken at various events about the cause. Massimo has been involved in efforts to fight the cause in partnership with the Clinton Foundation. The Opioid Crisishosted a discussion on the issue.

“Kianni's dream of transforming patient care continues to come true today as he works with lawmakers in Washington, D.C. to influence public policies that support innovation and promote good medical decisions,” according to his biography on the foundation's website.

The foundation hosts the summit every year, including a speech by Biden, who was vice president at the time, in 2015. Biden told the audience that he has sought out many of Kiani's input on medical technology because he has seen firsthand how much trauma and hardship people go through. Biden lost his wife and daughter in a car accident, and his eldest son, Beau, later died of brain cancer.

Kiani, who has an estimated net worth of $1.1 billion, endorsed Irvine Rep. Katie Porter's bid for U.S. Senate. effort He passed a bill to remove California Governor Gavin Newsom from office in 2021. He also launched a civic engagement platform called “A Starting Point” with actors Chris Evans and Mark Kassen.

The 59-year-old Iranian-born executive has taken on one of the world's most powerful technology companies. Masimo sued Apple in 2020, accusing the tech giant of stealing its technology and using it in the Apple Watch. The company develops wearable health devices, sensors and other products.

Dotsie Bausch, an Olympic silver medalist and former competitive cyclist, first met Kiani more than a decade ago after using a Masimo pulse oximeter, which measures oxygen levels in the blood. Bausch, who now runs the nonprofit Switch4Good and consults for Kiani's company, said the two bonded over their love of sports and a common work ethic.

Bausch said he didn't know how Kiani became close friends with Biden, but described the entrepreneur as a “giving person” who “cares deeply about people.”

“He's not just a CEO who wants to make a lot of money,” she said.