Redistricting is the redrawing of boundaries for legislative districts to reflect changes in population. Redistricting and reapportionment, the allocation of seats to states, help determine the partisan makeup of our legislative bodies, and strongly affect the representation of ethnic groups and geographic areas within the state. The high political stakes of redistricting and reapportionment have led to recurring struggles over control of the process in California. With the passage of Proposition 11 (2008) and Proposition 20 (2010), the responsibility for determining district boundaries was entrusted to the Citizens Redistricting Commission (California Constitution, Article XXI). Every 10 years, following the national census, the commission undertakes the redistricting process.
In 2011 the commission certified a set of maps establishing the boundaries for the reapportionment of the Assembly, Senate, Congressional, and Board of Equalization districts. Republican leaders accused the Commission of bias when drawing the Senate boundary lines and formally declared their opposition to the maps for those districts. Both supporters and opponents of the new districts worked to place Proposition 40 on the ballot to decide the issue. In the meantime, proponents petitioned the California Supreme Court to determine the legitimacy of the maps. In Janauary 2012, the court ruled that the Senate maps complied with the criteria set forth in the Constitution. Furthermore, the court ruled that election officials must use the commission drawn maps even if Proposition 40 was placed on the ballot. On February 24, 2012, the California Secretary of State's office announced that the measure had qualified for the ballot.
With Proposition 40 , voters can approve or reject the Senate district boundaries certified by the Citizens Redistricting Commission. If the measure passes, the Senate district lines will be used until the next redistricting process in 2020. If the measure does not pass, the California Supreme Court would appoint "special masters" to establish new Senate boundaries in accordance with the criteria specified in the Constitution. The court would then certify the new district boundaries, which would be used until the next redistricting process in 2020.