California had its first non-partisan open primary this year. Under the new election rules, all candidates, regardless of party run on a single ballot in the primary. The top two candidates are then selected, regardless of their party affiliation, to face off in the general election. In its first year of implementation, the California non-partisan open primary (also known at the "top-two" open primary) has led to the most competitive elections in the country, according to Ballopedia:

California's legislative elections in 2012 are more competitive than most of the country, based on Ballotpedia's Competitiveness index which captures the extent of electoral competitiveness exhibited in state legislative elections.

Some well-known political consultants and commentators have dismissed the success of the new primary rules, largely based relative low voter turnout in the primary and the fact that few independent candidates will be on the general election ballot. But, the Independent Voter Project, the organization that authored the "Top-Two Primary Initiative" in 2010, has pointed out that the open primaries were never about voter turnout, but about giving all voters a meaningful vote when the most people vote: the general election.

For example, in several heavily partisan districts, there are two candidates from the same party facing off in the general election. Under the old rules, these elections would have already been "decided" during the primary, when very few people vote. Now, although the candidates are from the same party, voters can choose which one is more likely to represent the general electorate.

Most Competitive Elections, More Resources:

Complete Open Primary Analysis of California's Open Primary Independent Candidates

State-by-State map of primary election rules

Arizona, the next state to adopt non-partisan primaries?

Steve Peace, co-Chair of Independent Voter Project and author of the CA's Open Primary Initiative discusses intellectual competition:

http://youtu.be/PCL9CKB7ns8