Two strong Democrats are seeking the California U.S. Senate open seat in 2016. They are Attorney General Kamala Harris and U.S. House Member Lorettz Sanchez. According to this story, both of them have been endorsed by a substantial number of California Democratic U.S. House members. The story mentions a recent poll of the entire electorate that shows Harris at 26% and Sanchez at 17%. Three fairly prominent Republicans have also announced for the seat, but none of them has as much voter support as 10%.
If the current California system is not changed before the 2016 election, there is a fair possibility that the U.S. Senate ballot in November would include Harris and Sanchez and no one else, and there is no write-in space in November for Congressional races. This would be the first time any statewide race in either of the top-two states excluded one of the two major parties.
California has not had a U.S. Senator from outside the San Francisco Bay Area since before the 1992 election. Part of Sanchez’ appeal may be a regional appeal. Harris lives in San Francisco.