Rep. Brian Bilbray (R-Calif.) has conceded defeat in his San Diego-area district, handing Democrats another pickup with just two intra-party races yet to be determined.

Bilbray trails San Diego Port Commissioner Scott Peters (D) by 3,877 votes. He called Peters to congratulated him and issued a statement acknowledging Peters' victory.

Rep. Brian Bilbray (R-Calif.). (AP photo)

"While Scott and I differed sharply on how to handle the issues facing our nation, now is the time to put those differences aside and find common ground to address our country’s many challenges," Bilbray said, according to the San Diego Union-Tribune.

Bilbray has served more than 12 years in Congress, returning to the chamber in 2006 by winning a hotly contested special election to replace jailed Rep. Duke Cunningham (R-Calif.). California's citizen redistricting commission drew Bilbray a swing district this year.

With the win, Democrats have now gained six House seats in the 2012 election, with the GOP's House majority reduced to 234-199.

Democrats also lead in the last two undetermined races, with Reps. Mike McIntyre (D-N.C.) and Ron Barber (D-Ariz.) holding small leads.

Reps. Charles Boustany (R-La.) and Jeff Landry (R-La.) will compete in a runoff next month in a merged district, but that race has no implications for the partisan balance of the House.