THE RECENT DECISION by the California Supreme Court to restore a ballot measure to reform the state's redistricting process gives California voters the chance to send a critical message in November. The initiative, part of a reform package being pushed by Gov. Arnold Schwarzenegger (R), had been stricken from the special election ballot by a lower court because of technical disparities between a version circulated among voters and a version given to the state attorney general. If passed, it would replace the state's corrupt system for drawing state and federal legislative districts with a cleaner one in which a panel of retired judges -- rather than the very politicians who have to run for office -- would draw lines without regard for protecting incumbents. By passing it, California voters not only would clean up their up own system but could spur reform elsewhere as well.

The initiative is not perfect. It not only creates create a redistricting regime for use after each decennial census; the new system is implemented immediately -- in the middle of a census cycle. Unlike the Texas mid-cycle redistricting, which Republicans undertook purely for partisan gain, California's would represent a genuine and valuable reform. But it would still legitimize the unfortunate principle that the Texas episode established -- that the drawing of district lines is fair game whenever one political bloc has the strength to reopen them, not just when new census data becomes available every 10 years.

Still, warts and all, passing the initiative would be a huge accomplishment. The advent of high-powered computing has made the old art of gerrymandering into a corruptly exact science. The result is that ever-more seats in state legislatures and in the House of Representatives have become safe for one party or the other. Many House elections are no longer even contested, so remote is the possibility of unseating an incumbent. In California's last election, as Mr. Schwarzenegger noted in a speech earlier this year, not a single one of 153 state or federal legislative seats changed party hands. "What kind of democracy is that?" the governor memorably asked.

The simple truth is that, as it's too often practiced in America, redistricting weakens two-party democracy and restricts all significant voter choice to primary elections within a district's dominant party. This, in turn, contributes to the polarization of the broader political system, as politicians of both parties attend more to keeping their flanks happy than to satisfying centrist voters or to reaching out to voters of the opposite party. For the largest state in the nation to declare this situation undemocratic and unacceptable and to demand instead that district lines get drawn as apolitically as possible would be an enormous step forward.