Mike Bloomberg just dropped out of the 2020 presidential race after pouring more than $500 million into his campaign and endorsed former Vice President Joe Biden.

Worth an estimated $58.4 billion, according to Forbes, Bloomberg was the richest person by far in the 2020 presidential race and the richest person ever to run for president.

The former New York City mayor has been in a relationship with Diana Taylor for 20 years, since they were seated together at a business lunch.

The 78-year-old billionaire’s longtime girlfriend, Taylor, is a 65-year-old former Wall Street executive and former New York State Superintendent of Banks. After Bloomberg announced his run for president in November 2019, she hit the campaign trail for her partner, who she was with throughout his three-term tenure as mayor of New York City.

Bloomberg's campaign declined to comment for this story.

Here's a look at Bloomberg and Taylor's 20-year relationship.

Mike Bloomberg just dropped out of the 2020 Democratic primary. The New York billionaire and his longtime girlfriend, Diana Taylor, have been together for 20 years.

Foto: The couple met two years before Bloomberg became mayor. Source: Bruce Glikas/Bruce Glikas/FilmMagic

The couple met in 2000 at a business luncheon, The Washington Post reported.

That same evening, they found themselves coincidentally eating at the same restaurant, Taylor recently told The Post.

"He looked at me and came over and said, 'Would you like to have a drink after this?'" Taylor told the Post. She said yes.

The couple lives in a five-story townhouse on New York City's Upper East Side that Bloomberg bought in 1986 for $3.5 million.

Foto: They've lived together in the townhouse for 19 years. Source: Mario Tama/Getty Images

According to New York Magazine, Bloomberg has often hosted dinner parties at the townhouse over the years. The parties "were often pretentious in their unpretentiousness," serving things like fried chicken and coleslaw, according to the magazine.

Bloomberg has also been buying up units in the neighboring brownstone for years and tearing down walls to combine the spaces with his primary home, The New York Times reported.

The couple has lived together for 19 years, Bloomberg told CBS' Gayle King in December 2019.

At the end of his last term as mayor, the billionaire spent at least $1.7 million renovating the home. Zillow estimates its current value at $17.7 million.

Taylor worked on Wall Street in the 1980s and went on to be appointed New York state's superintendent of banks by Gov. George E. Pataki in 2003.

Foto: Pataki, Taylor, and Bloomberg at a charity event in NYC in 2013. Source: Donald Bowers/Getty Images for Cancer Research Institute

Taylor has an MBA from Dartmouth University and a public health degree from Columbia University.

Throughout her career, her roles have included deputy secretary to former New York governor George Pataki, superintendent of banking for the State of New York, managing director at Wolfensohn Fund Management, vice president of KeySpan Energy, and vice chair of Solera Capital, a women-owned private equity firm.

New York Republicans once encouraged Taylor to run for Senate against Kirsten Gillibrand, but she ultimately declined - even though she thought she would win, she told the Observer in 2011.

"It was the thought of actually having to go and do that job, that was really not all that appealing," she said.

During Bloomberg's three-term tenure as mayor of New York City, Taylor was known as "The First Lady of New York," despite the fact they're not married.

Foto: Bloomberg was mayor of New York City from 2002 to 2013. Source: Andrew Toth/Getty Images for The Museum of Modern Art

Taylor has said she hates being referred to as Bloomberg's "gal pal" and that "girlfriend" isn't quite the right word either.

"I hate 'girlfriend' because it sounds so temporary," Taylor recently told the Post. "It's very junior high ... Nobody's come up with the language around what we are."

Today, Taylor sits on the board of several companies including Citigroup and Sotheby's.

Foto: Taylor has an impressive résumé. Source: Nathan Morgan for the Washington Post

She's also on the board of directors for Brookfield Asset Management and chairs the boards of the Hudson River Park Trust and charitable organizations Accion and Hot Bread Kitchen.

She also spent weeks on the campaign trail for her longtime partner, telling people why she thought Bloomberg would make a good president.

Foto: Taylor at a campaign rally in NYC in January 2020. Source: Scott Heins/Getty Images

"He believes in healthcare for everybody at an affordable rate, he believes in combating climate change, he believes in education, he believes in all the things that I think everybody wants for themselves and their families," Taylor said at a recent campaign stop in Colorado.

"The Republican Party has gone way to the right, and (Bloomberg's) values are now more affiliated with the Democrats than they are with the Republicans. But he has not changed his values one iota," she said.

Taylor has also revealed humanizing tidbits about her partner, such as that his favorite dinner is Shake 'n Bake chicken.

Taylor has high-profile friends that include Vogue editor-in-chief Anna Wintour.

Foto: Taylor and Wintour at a Vogue dinner in NYC in 2007. Source: BILLY FARRELL/Patrick McMullan via Getty Images)

"Her famous boyfriend may be the least interesting thing about her," Wintour recently told the Post, adding, "She's intelligent, independent - and completely her own person. Michael is lucky to have her."

Bloomberg and Taylor have been photographed together at events around the world, from the exclusive weeklong Sun Valley Conference in Idaho ...

Foto: Bloomberg and Taylor in Sun Valley, Idaho, in July 2019. Source: Drew Angerer/Getty Images

... to the US Open ...

Foto: Taylor and Bloomberg at the US Open in 2018. Source: Jean Catuffe/GC Images

... to equestrian events in the Hamptons.

Foto: Bloomberg and Taylor at an equestrian event in the Hamptons. Source: Sonia Moskowitz/Getty Images

In 2019, Bloomberg took both Taylor and his daughter, Georgina Bloomberg, as his dates to the Met Gala in New York City.

Foto: Taylor, Bloomberg, and his daughter, Georgina Bloomberg, at the 2019 Met Gala. Source: Dimitrios Kambouris/Getty Images for The Met Museum/Vogu

The former New York mayor had said that if he won the presidency, Taylor would be the "de facto First Lady."

Foto: Bloomberg and Taylor at the 2018 Met Gala in NYC. Source: Neilson Barnard/Getty Images

In a December 2019 interview with CBS' Gayle King, King asked Bloomberg if Taylor would be the country's "de facto first lady" and if she was playing a role in his campaign.

"She's playing a role in the campaign, number one," Bloomberg said. "Number two, we've only been living together for 19 years. And I think it's fair, if I can speak for her as well, neither of us have any plans to change."

King pressed him to answer whether or not Taylor would be the "de facto first lady" if he's elected.

"Oh yeah, of course," Bloomberg responded. "She would do the ceremonial things that Donald Trump's wife does."

When King asked whether he and Taylor would ever get married, Bloomberg said he wouldn't discuss that subject.