California Republicans are struggling this year to find a candidate that can beat Gov. Jerry Brown, state polls show. That's partly due to Brown's popularity and partly due to the shrinking proportion of the state's voters registered as Republicans.
About 28.6 percent of the state's voters are registered as Republicans, down from 35.7 percent a decade ago, according to the latest figures from the California Secretary of State. The proportion of voters registered as Democrats -- 43.5 percent -- has fluctuated during that period but today stands equal to where it was in 2004.
The percentage of voters declining to state a party preference -- 21.1 percent -- has grown significantly. If the trends of the next decade mirror the last, "no party preference" voters will outnumber Republicans in California by 2024.
Traditionally Democratic areas like San Francisco and Marin counties saw the largest proportional drop in Republican voters. No county in the state is now majority Republican. Only two small counties -- Lassen and Modoc -- increased the proportion of voters registered as Republicans over the last decade.
This map shows the change in the rate of Republicans -- Republicans per 1,000 registered voters -- from 2004 to 2014.