Rep. Scott Peters (D-San Diego) appears close to defeating Republican challenger Carl DeMaio after a costly campaign marked by biting accusations.
The Associated Press has declared Peters the winner.
Peters, seeking a second term, is ahead by 4,491 votes although an estimated 10,000 votes have yet to be counted, according to the county elections department.
Peters has not declared victory and DeMaio has not conceded defeat. But their backers are declaring Peters the winner in the 52nd Congressional District.
The House Majority Political Action Committee, dedicated to electing Democrats, said that Peters will “be able to continue his great work in Washington.”
The editorial page of the U-T San Diego newspaper, which ran three editorials endorsing DeMaio, said Peters is the apparent winner. The editorial page praised DeMaio and hoped that he will remain in local politics.
In Northern California, Rep. Mike Honda (D-San Jose) declared victory Friday in his bruising battle with fellow Democrat Ro Khanna. Khanna conceded a few hours later.
Also Friday, election officials released some updated tallies in other House contests around the state, some of which remain too close to call.
In Ventura County, Rep. Julia Brownley (D-Westlake Village) widened her lead, to 1,028 votes, over Assemblyman Jeff Gorell (R-Camarillo).
For other endangered Democratic congressmen, the news was not so good. Rep. Ami Bera (D-Elk Grove) continued to trail former Republican Doug Ose of Sacramento, by 2,183 votes.
And in the biggest surprise of the congressional races, Democratic Rep. Jim Costa of Fresno was running behind dairy farmer Johnny Tacherra, but on Friday Costa had moved to within 78 votes of Tacherra.
In another unexpectedly close race, Rep. Jerry McNerney (D-Stockton) was holding on to his lead over Republican activist and retired U.S. marshal Tony Amador.
In San Diego, on election might, DeMaio held a 752-vote lead. But when late-arriving mail ballots started to be counted, the trend was clearly for Peters.
By Thursday night, Peters had an 861-vote lead, and by Friday night the lead grew to 4,491. Another tally is expected late Saturday afternoon.
The 52nd District includes Poway, Coronado and a northern stretch of San Diego. Registration is roughly split among Democrats, Republicans and independents.,
Peters, 56, an environmental lawyer and former San Diego City Council member, defeated Republican incumbent Brian Bilbray in 2012.
DeMaio, 40, a former City Council member, was defeated for San Diego mayor in 2012.
The dueling sides spent more than $10 million in the campaign. Peters accused DeMaio of being a tea party follower who would slash public services.
DeMaio accused Peters of pushing the city toward bankruptcy while on the council. Two former campaign staffers accused DeMaio of sexual misconduct.