Well, there would obviously be a large influx of refugees into Oregon, Nevada, Arizona, as well as other Western states (California's Mormons would probably emigrate to Utah, which could significantly increase its population). California would definitely lose a good amount of electoral votes, but it probably stays Democratic (though it'll probably be less so). As the affected areas are mostly liberal, I think the states around California shift blue (this is most significant in Arizona, but less so in Nevada and Oregon).
Assuming Californian emigration is exacerbated, and natural disasters are fresh in western voters minds, this could have interesting implications for Montana and Idaho as well! For the first time in history, those libertarian voters might be more receptive to a hands-on federally-funded and/or managed approach in dealing with disasters.
Personally, as a Coastal Californian in the current diaspora, I wound up in the Sun Belt. I know that's the main target for Californians, but I've heard a big chunk- particularly those whiter and more well-off- are heading to northern states. Fresh air and acreage and whatever.
