The town of Atherton, California has only 7,000 residents, but it’s home to enough titans of the tech industry to field a polo team: Sheryl Sandberg, Eric Schmidt, Meg Whitman, Tim Draper and Marc Andreessen are just some of the Silicon Valley suburb’s rich and famous. When the former deputy prime minister Nick Clegg decamped from British public life to Facebook public relations, he traded a townhouse in Putney for a $9m estate in the exclusive enclave.

The richest zip code in the United States, Atherton is home to those who know how to bet on the right horse. And yet the presidential candidate of choice in this sanctuary for the 1% is one who has yet to come close to the top of the polls: the New Jersey senator Cory Booker.

Americans who live in the country’s 20 wealthiest zip codes have donated the most to the moderate Democratic presidential candidates Kamala Harris, Pete Buttigieg, Booker and Joe Biden, a Guardian analysis of presidential campaign finance filings for the first nine months of 2019 found.

The vast majority of the fundraising from the 20 wealthy areas went to Democrats. Residents of these bastions of actual limousine liberals – including Westchester, New York, Beverly Hills, and Greenwich, Connecticut – have ponied up nearly $880,000 for Senator Harris and nearly $600,000 for Mayor Buttigieg. Booker and the former vice-president Biden raised more than half a million dollars each.

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Donald Trump cashed his share of checks, too. The president raised more than $500,000 in total across the 20 locales, and was the top recipient in three: Palm Beach, Florida; Newport Beach, California; and Bedminster, New Jersey. Trump spends significant time at his private club Mar-a-Lago in Palm Beach and his golf club in Bedminster.

Meanwhile, the senators Bernie Sanders and Elizabeth Warren, who are among the frontrunners nationally, have amassed the largest campaign war chests of all the Democratic candidates while refusing to hold high-dollar fundraisers and calling for higher taxes on the wealthy. Their aversion to the rich appears to be reciprocal.

Sanders, who has raised the most of all Democratic candidates this cycle, has received just $59,130.05 from donors in these areas. Warren brought in slightly more than $160,000.

The Guardian’s analysis does not include every donor because campaigns are not required to report contributions from those who gave less than $200 in total. We used data from the Internal Revenue Service to identify those zip codes with at least 1,000 tax-filing households and the highest average adjusted gross income.

Booker’s haul in Atherton – $95,650 – tops Sanders’ total across all 20 zip codes. The former mayor of Newark also topped the list just north of San Francisco in Marin, and in a number of wealthy suburbs of New York City – Westchester, New York; Short Hills, New Jersey; and Old Westbury, New York.

Harris was a close second in Atherton, and the California senator also came out first in other elite neighborhoods in her home state: Palo Alto; downtown San Francisco; Century City, Los Angeles; and Beverly Hills. She also topped the list for Tribeca in New York City.

Though Buttigieg brought in the second-highest amount of total fundraising from the 20 wealthiest zip codes, he only topped the list in Greenwich, Connecticut – a bastion of New England blue blood and the childhood home of George HW Bush.

What about the other 99%?

Of course, political donors in these zip codes only represent a tiny fraction of the American public – and account for less than $4m of the hundreds of millions of dollars that have already been donated to 2020 presidential candidates.

We did the same analysis of the poorest 20 zip codes with at least 1,000 tax filers – a list that includes poor neighborhoods in cities such as St Louis, Missouri; Erie, Pennsylvania; Tallahassee, Florida; and Cincinnati, Ohio. Across all 20 areas, campaigns have reported just 28 donors, for a total of $7,113.31.

Sanders was the clear favorite, bringing in nearly $3,200 from 12 donors, followed by Trump ($965) and Andrew Yang ($894).

We also looked at political fundraising by residents of major metropolitan areas – where the majority of Americans live.

These results demonstrate a distinct home-field advantage. Harris, of California, wins out in San Francisco and Los Angeles, while Warren, of Massachusetts, takes the prize in Boston and New Jersey. New Jersey’s Booker tops the list in neighboring New York City. Buttigieg, a midwestern mayor, performed best in Chicago.

Trump swept a number of major cities across the southern half of the US, racking up the most money in Miami, Atlanta, Dallas, Houston and Phoenix, Arizona. Beto O’Rourke was the top Democratic fundraiser in both Dallas and Houston, while Biden led Democrats in Atlanta and Miami and Sanders won the most Democratic support in Phoenix.