There are virtually no places where Republicans win a D+11 district. So how'd this happen?
We should remember that the election was held in May, not November. In the past, we've seen that June primaries are a lot more Republican than November general elections. Last year the difference was 15.3%. So a 10% Vidak win in May might be a 5% loss in November.
This is the Central Valley. I've said it before and I'll say it again, Republicans do very well down ticket in the Central Valley. In fact, David Valadao actually won the overlapping CA-21 by more points in the general election than he did in the primary in 2012. Yes, while other Republicans lost 15% off their margin, Valadao actually increased his. Presidential numbers aren't very relevant when looking at the Central Valley. You're much better off looking at more local races. Of course, Michael Rubio did win big in 2010. That's evidence that with a good candidate Democrats can win in the Central Valley, but it's also true that Republicans didn't really challenge him hard there. Valadao was winning his assembly district with a similar 61%.
Vidak winning wasn't that much of a surprise, although getting over 50% certainly was. This won't really impact Democratic majorities in Sacramento. It only gives Republicans 12 senate seats. They need 14 to end the Democratic super majority. What'll, temporarily, end the Democratic super majority in the assembly is the impending resignation of Bob Blumenfield to take an LA City Council seat. Democrats will regain their super majority again after an upcoming special election but then may lose it again because Assemblywoman Holly Mitchell is expected to run for and win state senator and soon to be LA City Councilman Curren Price's senate seat.
What does this mean for the 2014 election? A lot really. After all, Democrats should do better in November 2014 than May 2013 when the electorate should be more than twice the size this one was. The new SD-14 that Vidak will run for is one where Obama in 08 and Barbara Boxer in 10 did 3.3% worse than this district. So Vidak doesn't have to be as strong to win there. Carly Fiorina won that district in 2010. In a mid-term non-Presidential year, any district Fiorina won is one where Republicans have a good shot of winning. Especially with an incumbent.