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Democrat Eric Swalwell, right, candidate for the 15th Congressional District, gives a victory speech with former congresswomen Ellen Tauscher, right, at his side during an election night party held in Pleasanton, Calif., on Tuesday, Nov. 6, 2012. Swalwell is running against incumbent Democrat Pete Stark. (Doug Duran/Staff)

Rep. Pete Stark, dean of California's congressional delegation, lost his seat to a fellow Democrat, thanks to the state's new "top-two" primary system, returns showed early Wednesday morning.

Stark, D-Fremont, won office 40 years ago by beating a seasoned Democratic incumbent whom he painted as out of touch with the times and his constituents -- just as challenger Eric Swalwell, 31, a Dublin councilman and Alameda County prosecutor, described Stark, 80, this year in the newly drawn 15th Congressional District.

At shortly after midnight, returns showed Swalwell beating Stark by about 6 percentage points.

"The votes tonight reflect the effort we put into the race and the enthusiasm all across the district," Swalwell said early Wednesday morning. "People were ready for a congressman who wanted to show up and work for them every day."

Stark's camp wouldn't cry "uncle," however.

"There are 358,915 voters in the district, approximately 130,000 votes have been counted, and we believe that every vote should be counted," Sharon Cornu, Stark's campaign manager, said shortly after midnight. "People stood in line tonight in San Lorenzo and Hayward to vote, and we want their votes counted."

A conservative independent candidate was eliminated in June's primary, leaving these two Democrats to duke it out in this general election.

Even with a radically redrawn 15th Congressional District, Swalwell's campaign initially seemed like a longshot.

But Stark's loose lips helped fuel Swalwell's run.

In April Stark accused Swalwell of accepting "hundreds of thousands of dollars in bribes" from Dublin developers seeking preferential votes -- a charge Stark retracted and apologized for eight days later. Other gaffes Stark made in the spring appeared to give momentum to Swalwell's contention that the Stark had been in Congress too long and had lost touch with his constituents, or even with reality.

By summer and fall, however, Stark, became more tight-lipped. And strong support from labor and Democratic establishments and a barrage of direct mail in September and October, helped Stark regain momentum.

Josh Richman covers politics. Contact him at 510-208-6428. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.