The congresswoman Karen Bass and the billionaire real estate developer Rick Caruso will head to a November rematch in their bids to become the next mayor of Los Angeles, after neither candidate secured enough votes to win outright in Tuesday’s primary.

An early tally of mail-in ballots showed Caruso with 41% and Bass with 38% of the vote, meaning both candidates failed to clear the 50% threshold needed to win outright. The Associated Press called the race as a runoff late on Tuesday evening.

As the top two vote-getters, they will advance to the general election in a contest whose outcome is likely to have major consequences for Los Angeles’s approach to policing, crime and the growing humanitarian crisis of homelessness across southern California.

While the non-partisan mayoral primary began with a field of a dozen candidates, it quickly became a contest between the two frontrunners: Bass, a former progressive community activist in South Central Los Angeles who had risen to become the chair of the Congressional Black Caucus, and Caruso, a luxury mall developer and former Republican who Forbes ranks No 261 on the list of the richest people in the US.

The mayoral candidates and their outside backers and critics poured more than $50m into campaign spending during the primary race, a stunning figure in a campaign whose central issue has been what to do about the more than 41,000 unhoused people living in Los Angeles.

Homelessness is a crisis along the entire west coast, but many voters and politicians in Los Angeles say it has reached a state of emergency. As of 2020, an estimated 40% of all unhoused people in California, and 20% of all unhoused people living outside in the US, lived in Los Angeles county. As rent and housing prices have continued to rise, the presence of people living in cars, RVs, and in tents on the street and in public parks has prompted fierce debates about the failures of city officials to resolve a growing humanitarian crisis.

Caruso, who has an estimated net worth of $4bn, poured more than $38m of his own fortune into his campaign through early June, with a pledge to “clean up” Los Angeles. He was backed by celebrity endorsements from his neighbor, the actor Gwyneth Paltrow; Bill Bratton, the police chief who championed “broken windows” policing; the rapper Snoop Dog; and the entrepreneurs Kim Kardashian and Elon Musk.

His omnipresent political advertising across Los Angeles won him enough votes to advance to the general election as the more conservative, pro-police alternative to Bass, a California Democrat who was considered as a potential vice-presidential pick for Joe Biden.

At his election night party at the Grove, one of his shopping malls, Caruso said the voters supporting him were sending a clear message: “We are not helpless in the face of our problems. We will not allow the city to decline,” the Los Angeles Times reported.

At Bass’s election party, with her grandson and other family members by her side, the congresswoman told supporters, “We are in a fight for the soul of our city, and we are going to win,” the Times reported.

Caruso ran a campaign focused on crime and disorder, pledging to strengthen and expand the city’s police department by hiring 1,500 additional officers. He drew scrutiny on a number of fronts, including his suggestion to arrest unhoused people who refuse to move to a city-provided shelter bed, his record of political donations to Republican candidates who have opposed abortion rights, and the fact that he only registered as a Democrat shortly before entering the mayoral race (he was previously a political independent, and before that, a Republican).

Bass, who first rose to prominence as an advocate for public health approaches to addiction and crime during the crack epidemic in the 80s and 90s, has said that she decided to run for mayor in part because of her concerns that voters’ frustrations over homelessness and high-profile property crimes might lead to the same kind of punitive, damaging policies that California politicians and voters endorsed during the 1990s.

Bass has highlighted the dangers of criminalizing poverty, even as she has pledged to put an end to unhoused people living in public spaces across the city. She has said she supports small increases to the city’s police force and a focus on devoting more police resources to solving the city’s homicides.

As Caruso faces off with Bass in the general election, it’s unlikely that Bass will fully match his spending, but progressive Hollywood donors are expected to pour a substantial amount of money into her campaign, as well.

“If Rick Caruso was willing to spend $30m in the primary, why wouldn’t he spend the same amount for the general?” the political scientist Fernando Guerra said.

Bass “will not meet or beat what Rick Caruso spends”, but her campaign and her liberal Democratic allies will spend enough “that she will be competitive in terms of getting her message out”, Guerra added.

To break national records for a self-financed mayoral campaign, Caruso would have to outspend the New York billionaire Michael Bloomberg, who spent $109m on his campaign to win a third term as New York City’s mayor in 2009. Bloomberg spent $74m in 2001 and $85m in 2005 on his earlier mayoral bids; he burned through a reported $1bn on a short-lived run for president in 2020.

The mayor’s race took place alongside other closely watched political contests in California on Tuesday. In San Francisco, the city’s progressive district attorney, Chesa Boudin, was recalled by voters in a blow to criminal justice reform.