Congressman Jim Costa, D-Fresno, added 994 votes to his lead over challenger Andy Vidak of Hanford as votes from Fresno County were announced Wednesday.
Costa's new lead stood at 2,422, outstripping the 1,823-vote lead Vidak held on election night more than two weeks ago.
Uncounted ballots in Kern and Fresno counties have come in sharply in Costa's favor since Nov. 3.
Vidak's home county of Kings offered him an extra 118 votes during the time frame. But Costa pulled in 4,363 more votes than Vidak in Kern and Fresno counties, sinking what looked -- on election night -- like a rare Republican victory over an incumbent in California.
But Costa chipped away at Vidak's lead and finally took a lead of his own on Nov. 10 -- and declared victory at that time.
Fresno County Registrar of Voters Victor Salazar said Wednesday that around 10,000 votes remained to be counted in Fresno County.
But, he added, "almost all of the 20th Congressional District has been processed."
Roughly 4,500 votes were left to count in Kern County and Costa has been winning here with 61 percent of the vote.
Vidak has not conceded Costa's victory. A spokesman for the Vidak campaign said Wednesday that the Kings County cherry farmer was contemplating some kind of statement about the results of voting.