Just looking at some recently published statistics worked up by the Sacramento Bee on California Congressional Districts, it seems pretty obvious to me that Republicans should end up with several more competitive seats than the Democrats will have, when the Redistricting Commission finishes its work. This is because it appears that, of California’s 53 Congressional districts, Democrats are "over-representing" (elected to districts that are populated by less people than there should be) by 5% or more in 22 seats statewide, of the "ideal" population of 702,905 in each district, while Republicans are "over-representing" by at least 5% in just 3 seats. All this over-representing has to be shaken out so that these seats get more voters, meaning in clusters there will be fewer districts. Some of the Democrat "over-representation" is in double-digits, as high as 13% for Democrat Xavier Becerra and 10.2% for Democrat Loretta Sanchez. (This is somewhat akin to being a U.S. Senator from Rhode Island!) It reflects demographic trends that might be called "de-urbanization." And the Democrats problem is their over-represented districts are largely all clustered together, such as Congressional Districts 28 through 39 in Los Angeles and Orange County, all twelve of these over-represented by more than 5% and all contiguous to each other and all represented by Democrats. The problem exists but is less pronounced for Democrats in the San Francisco Bay area, where Congressional Districts 6 through 9, and 12 through 17, ten districts total, are all contiguous, have all Democrat incumbents, and are all "over-represented," though a little less than the southern California Democrat districts. Bottom line? Los Angeles County and the San Francisco Bay area are truly "over-represented" in Congress, and the reapportionment MUST adjust downward for that.
In contrast, Republican Mary Bono’s district is "under-represented" by a startling 30.1%, representing demographic trends of people moving into her district in a significant manner. Republicans in general represent less people than they should be representing as a result of the last Census, in 13 districts across the state. Democrats are elected in only 5 districts that are under-represented, and only three of these are significant: McNerney (13.4%), Filner (7.8%), and Jim Costa (5.9%). It is interesting that of these three, both McNerney and Costa had re-election troubles last year. A fair reapportionment should make matters worse for them, and result in additional pickups in inland and Central Valley areas to account for demographic trends; which will empower currently under-presented voters in rural and suburban areas, and Republicans, if the California GOP can get its act together.