I disagree. 2010 was a strong republican year, Boxer has never been very popular and California (and the USA) were less radical in 2010 than in 2015. Remember when Obama was in favor of civil unions instead of gay marriage?
Indeed it was a strong republican year, for most of the country, but California was never seriously in play after September of that year. Like I said... it's D+15 out there. There's no overcoming that.