With 100% of precincts reporting Wednesday morning, Hahn outpolled Napolitano in the District 4 race, 47% to 37%.

In a second county contest, Kathryn Barger, chief of staff to the current supervisor, secured a runoff spot for the District 5 seat with 30% of votes cast.

Darrell Park, a former White House Office of Management and Budget staffer, moved into second place in later returns and finished 417 votes ahead of the third-place finisher, state Sen. Bob Huff, each with about 15% of the vote.

The results are unofficial until late mail-in and provisional ballots are counted.

This year’s election represents the second phase of a major shift on the Board of Supervisors brought on by term limits approved by voters in 2002.

Departing supervisors Don Knabe and Michael D. Antonovich have been on the board for decades. Knabe was first elected in 1996 and Antonovich in 1980. They are the only two Republicans on the officially nonpartisan five-member board.

Eight candidates were on the ballot in the race to replace Antonovich: Barger, Huff, Park, Los Angeles City Councilman Mitch Englander, prosecutor Elan Carr, former Glendale Mayor Ara Najarian, Palmdale-area real estate investor Raj Pal Kahlon and Altadena Town Council member Billy Malone.

Park, Kahlon and Malone are Democrats. The other five are Republicans.

Englander and Barger had led the pack in fundraising, each raising more than $1 million through their campaign committees and also receiving substantial support from independent expenditure committees. Unions representing county firefighters and sheriff’s deputies put $1.2 million into an outside committee set up by the Los Angeles County Federation of Labor to back Barger’s bid.

At Barger’s election night party at a restaurant in Pasadena with Antonovich and a crowd of supporters, Barger noted the importance of faith-based groups in the Antelope Valley and the nonprofit communities in Santa Clarita and the San Gabriel Valley in supporting her campaign. She also acknowledged the boost her campaign got from labor.

“They know that my word is good,” Barger said about getting the endorsement of the labor federation. “If I don’t agree, I’ll give you the reasons why I don’t, but I will always listen and in areas where compromises can be made, I will.”

Park said he does not expect the vote tally to be finalized until later in the week, but said he was encouraged by the results.

“It goes to show you, in this cynical time in our politics, everyone thinks it’s only big money that matters, and it’s not true,” he said.

Park, who runs a start-up called Better Than We Found It and advises green energy companies, raised about $200,000, hundreds of thousands less than the Republicans in the race. He said he thought the fact that he was a Democrat and endorsed by the county Democratic Party gave him a boost in the district, where registered Democrats now outnumber Republicans, 41% to 30%.

“We didn’t have to come up with a message that makes us into something we aren’t,” he said.

Huff, who had held a slim edge for second place in early returns, said Tuesday night he thought his record of working across party lines in Sacramento had helped him compete with better-funded opponents.

“There’s something to love and hate about my record, because it’s so public,” he said.

Huff noted Wednesday morning that there were still thousands of votes to be counted, including mail-in ballots sent on election day.

“It’s close, and we’ll just stay tuned,” he said.

Englander, who had been expected by many to make the runoff, finished fifth with about 12% of the vote.

As his supporters watched the results roll in at the Angeles National Golf Club in Sunland, Englander said the county election and other local races had been overshadowed by the presidential contest.

In the race to replace Knabe, Hahn, a former Los Angeles city councilwoman and daughter of longtime former county Supervisor Kenneth Hahn, was widely considered the favorite, with some predicting she would win outright Tuesday.

She faced off against Napolitano, a Knabe aide and former Manhattan Beach city councilman, and Whittier school board member Ralph Pacheco. Napolitano is a Republican; Pacheco is a Democrat.

Napolitano now will face Hahn in November. He and Hahn each raised more than $1 million as well – Napolitano by putting in more than $760,000 of his own money and Hahn through substantial support from both public and private-sector unions.

With early returns showing her in the lead, Hahn said she would be honored and humbled to serve in a post that her father held for decades.

“I’ve always felt that I’m going to win this,” she said Tuesday night. “It’s either tonight or it’s going to be in November.”

Napolitano said he was pleased with the momentum his campaign had gained despite beginning with much lower name recognition than Hahn.

“We just did an old-school campaign, reaching people and talking about the issues and about records,” he said.