The June 8, 2010 election is a statewide direct primary election: voters from each political party nominate candidates from their party to run in the November general election.
California has a modified closed primary system. That means, if you registered with a qualified political party, you may vote only for candidates from that party in partisan contests (e.g., Governor, U.S. Senate). If you did not register with a qualified political party, you may vote in partisan contests if a party allows unaffiliated voters to participate.
For the June 8, 2010 primary, two political parties allow unaffiliated voters to vote their party’s ballot for all contests except County Central Committee:
The Democratic Party
The Republican Party
          All voters, regardless of party affiliation, may vote in nonpartisan contests (e.g., Superintendent of Public instruction, Superior Court judge) and on ballot measures.