With 88% of the expected vote in, ABC News projected Hilton's advancement on Tuesday afternoon.
Matt Mahan and Antonio Villaraigosa dropped out of the race early in the evening as the early results were announced. After more of the votes were counted, Katie Porter also conceded.
Hilton faces a challenging electorate in the November election, as California has nearly twice as many registered Democrats as Republicans. If elected he would be the first GOP candidate to win statewide office since 2006.
He thinks he can beat the odds.
"Change is coming to California," Hilton said the day after the election. "That is good news for everyone."
The outcome means Democratic candidate Tom Steyer did not qualify for the November election.
During the campaign Hilton attacked Democrats over the state's high cost of living, the homelessness crisis and other issues. He pledged to lower prices for everything from gas to housing; make Californians' first $100,000 free of income tax; create a loan program for first-time homebuyers; and freeze in-state tuition at public colleges.
Hilton was endorsed in April by President Donald Trump, which helped him consolidate support among Republican voters in the primary but could be a liability in the general election.
Hilton, who has never held elected office, came to the United States in 2012 from the United Kingdom, where he was an adviser to Conservative Party officials including former Prime Minister David Cameron. He had a show on Fox News from 2017 to 2023 and became a U.S. citizen in 2021.
Hilton often mentions his parents' experience fleeing communism in Hungary before migrating to the U.K. as a formative part of his family's history that helped shape his conservative worldview.
Steyer has put more than $216 million of his personal fortune into his campaign.
The Associated Press contributed to this report.
Stay with us for the latest details on this developing story.