California is moving into uncharted political territory by charging a citizens' commission with the task of drawing boundaries for its congressional, state Senate and Assembly districts.

In short, nobody knows what is going to happen.

But experts say this much is certain: The grand experiment -- which is being watched closely by other states -- likely will benefit the San Joaquin Valley.

A study issued this month by a Southern California think tank says the region between Sacramento and Bakersfield has grown so much that it should pick up a new congressional seat -- as well as additional representation in the state Legislature.

At the same time, the study said, the new seat likely would come at the expense of the Bay Area, where population growth has lagged behind the San Joaquin Valley.

Some Valley lawmakers say additional seats in Congress and the state Legislature could give the region badly needed leverage to push its political agenda.

"It's very important to get an additional member," said Rep. Devin Nunes, R-Visalia. "It's one more vote [for the Valley] -- and one less for the Bay Area."

The study -- done by the Rose Institute of State and Local Government, a nonprofit at Claremont McKenna College in Southern California -- projected the state's population and assumed it would retain its 53 congressional seats. It then established the ideal population size for congressional, state Senate, Assembly and Board of Equalization seats.

Using that model, it showed all six Valley congressional districts exceeded the projected target population of 705,604. Because districts must have about the same number of residents after redistricting, this means the Valley is likely to get another district. The surpluses ranged from 51,335 in the 21st Congressional District, represented by Nunes, to 89,752 for the 11th District, which runs from Stockton into the far East Bay suburbs.

At the same time, 10 districts that make up almost all of the Bay Area would need a significant number of additional residents to reach the norm, meaning the region is likely to lose a district. For instance, the Rose Institute study found San Francisco Democrat Nancy Pelosi's seat to be more than 121,000 below the target population.

"The trends have been visible for a while," said Douglas Johnson, one of the study's authors. "Even with foreclosures and people possibly moving back [to coastal areas], it's not going to overcome the massive [inland] growth of the first eight years of the decade."

The Rose Institute study came just ahead of the planned Tuesday release of the first 2010 census numbers for the nation and the states, as well as the number of congressional representatives allocated to each state.

Some recent census estimates indicate that populations in coastal districts may not have shrunk as much as the Rose Institute report suggests.

Still, demographers generally agree that the inland parts of California -- both in the San Joaquin Valley and the Inland Empire of Riverside and San Bernardino counties -- have grown at a faster clip than coastal areas since the last census was conducted 10 years ago.

Mary Heim, chief of California's demographic research unit, said the state's population has grown 14% in the past 10 years. During that period, she said, San Joaquin Valley counties have grown faster than the state average, while growth in the coastal counties was below the average.

Change is coming

The key to the once-a-decade reapportionment process that will grow out of the census, everyone agreed, is the commission. It is made up of a mix of Californians -- Republicans, Democrats, third-party and independent voters.