To any third-party voters in California who were planning to wait until November to vote for Libertarians, Greens, American Independents or anybody who isn't a D or an R: Drag yourself out to the polls today or you'll likely miss your chance.
Today's primary marks the implementation of Proposition 14, passed in 2010, which opens up state races to a "Top Two" runoff system. Candidates for U.S. Senate and Congress, State Senate and Assembly and all statewide constitutional offices are presented in an open slate. Primary voters can choose among the candidates regardless of their party. The top two candidates will face off in November, again, regardless of their party.
The change doesn't affect the presidential race, but anybody hoping to protest the tyranny of the two-party system in California needs to now do so in the primaries. Many third-party candidates are not going to make it to the November ballot.
Third-party candidates opposed the proposition in 2010, but it passed by a slight margin. We'll see how the Democrats and Republicans feel about it if vote-splitting results in absurd outcomes, like two Democrats facing off for Congress or Assembly in a primarily Republican district. It's possible from today's vote for Sen. Dianne Feinstein to end up facing another Democrat with no Republican or third-party alternatives come November.
Brian Doherty covered the Prop. 14 battle in 2010. As he pointed out, it has effectively kept third-party candidates off the ballot in Washington State (which adopted the system in 2008) and made it easier for incumbents to keep their seats.