The three most prominent Republicans running for U.S. Senate in California this year all express the opinion in this San Francisco Chronicle article that none of them are likely to qualify for the November 2016 ballot. These three Republicans are Ron Unz, Tom Del Beccaro, and Duf Sundheim. Polls indicate that the top two vote-getters in June will be Democrats Kamala Harris (Attorney General of California) and Loretta Sanchez (U.S. House member from Orange County).
The only debate for U.S. Senate in California includes the five candidates mentioned above, but none of the other 29 candidates who are also on the June ballot.