has there ever been a presidential nomination race where California was this important?
Important is an interesting word, but the last time CA's primary mattered for the Republican's was 1976 when Reagan beat Ford, but still lost the nomination. Some argued that it both cost the R's the 1976 general election and setup Reagan for the win in 1980.
For the Dem's it was 1972 when McGovern clinched over Humphrey. Back then the CA primary was winner take all and CA was a huge deal. Now both parties split the delegates based on votes and CA no longer sways the parties one way or another.
I would argue, however, that the most important Primary in CA history was RFK in 1968. After winning and perhaps securing the nomination, he was assassinated leaving the hotel post victory speech.
for the Dems, it's over. even if Bernie gets 70% of the remaining votes, he doesn't close the gap.
Please tell me that you did not just figure this out because of this interactive map...