Last night Democratic Orinda Mayor Steve Glazer scored a relatively easy win in the 7th state senate district race against Democratic Assemblywoman Susan Bonilla. Glazer is considered a pro-business moderate and he faced stiff progressive/union opposition. His win is just the latest for California progressives. The most Democratic districts are frequently majority minority and elect minorities. Those candidates are sometimes progressive but don't tend to put as much a priority on issues like environment. Progressives have a tough time winning in swingy/light blue districts because there's too many moderate voters.
The bread and butter for progressives used to be districts Obama won with 60-70% of the vote. When there were party primaries a progressive would beat the moderate and then win that and then win the general election against a Republican. The current system is Top Two. In this system all candidates run in all party primary. Districts this blue don't attract strong Republican candidates and often result in two Democrats finishing top two. Then Republicans choose between two Democrats in the general election. And Republicans will choose a moderate like Glazer.
This is less a problem for Republicans because Republican districts tend to be less red than Democratic districts are blue. Thus, you get a Democrat finishing second in the primary and a conservative can win the general election. In the instances where two Republicans do make top two, however, Democrats do have a big role in selecting who wins and that can sink the more conservative candidate too.