Democratic Rep. Ellen O. Tauscher confirmed just Wednesday that she has been offered a high-level State Department post in the Obama administration — and prospective candidates already are stepping in or taking themselves out of contention to succeed her in California’s 10th District seat.

According to one local Democratic Party official, state Assemblyman Tom Torlakson will not be a candidate for the pending special election in the 10th District, which includes cities such as Fairfield, Antioch, Livermore and part of Concord in the East Bay suburbs of San Francisco.

Chuck Carpenter, the Democratic Party chairman in Contra Costa County — which includes most of the 10th District’s population — told CQ Politics Thursday that Torlakson told him he would remain in the race he has already launched for state superintendent of public instruction, which would put him in charge of California’s school system.

Torlakson could not immediately be reached directly for comment.

Torlakson’s decision not to run for the House does not preclude a competitive multi-candidate race for the Democratic nomination, which is likely to be decisive in a strongly Democratic-leaning district that gave 65 percent of its 2008 presidential vote to Barack Obama .

Carpenter said two well-known regional Democratic officeholders, state Sen. Mark DeSaulnier and state Assemblywoman Joan Buchanan, have expressed interest in the seat.

Many state lawmakers are likely to consider running, given the term limits placed on them by state election law. “An open seat like this is a big opportunity to move on and especially into Congress where of course there are not term limits,” said Henry E. Brady, a political scientist at the University of California at Berkeley.

Any candidate activity is just positioning for now, as the seat will not become vacant unless and until Tauscher — elected last November to a seventh House term — is confirmed by the Senate to be undersecretary of State for arms control and international security.

Tauscher is a Democratic moderate who has focused strongly on defense and foreign policy issues and currently serves as chairwoman of the House Armed Services Subcommittee on Strategic Forces. She has drawn no major flak since her nomination was revealed Wednesday.

Should Tauscher vacate her House seat, Republican Gov. Arnold Schwarzenegger would call a special election in which candidates of all parties would run on a single ballot. If one candidate receives a majority in the primary, he or she would be declared the outright winner. In the absence of a majority winner in the primary, the top vote-getter in each party would advance to a special general election.

Republicans don’t have a deep bench of elected officials in this district. One whose name has been floated as a possible House candidate is San Ramon Mayor H. Abram Wilson, who lost a bid for state Assembly last fall.

But GOP strategist Tim Clark said his party should be able to produce a serious candidate. He said he believes self-funding Republicans, possibly technology-industry millionaires, are most likely to dominate the GOP field.

“I’ve been contacted by no less than three self-funded Republicans in the last six years who wanted to look at that seat,” Clark said. He declined to offer names, saying he would need to speak with the individuals involved before divulging that information.