Lightly populated Idaho and Wyoming remain strongly Republican, as does Utah. And Democrats are struggling in Arizona, where a bruising immigration debate has given Republicans a lock on statewide offices but may provide Democrats an opening by firming up their support among the state’s growing Hispanic population. Still, the overall trend is clear, according to analysts on all sides of the political spectrum.

“It’s just a different world,” said Bill Carrick, a veteran Democratic strategist in Los Angeles who has worked widely in the region. “Nevada became the next California and now Arizona looks like it will become the next Nevada. … It’s just pushing the West further and further from Republicans.”

The shift is due to a combination of factors: the fusion of the region’s libertarian spirit with both an influx of transplants from more liberal states seeking a better quality of life, and a growing immigrant population alienated by increasingly hardline Republican immigration proposals…

But [Teixeira] argued in an interview that what’s happened to the West is not very different from what’s taking place across the country. Surveys for his book last year found it only slightly more libertarian on social issues and holding similar views toward government and taxation as other parts of the country. That, he said, is bad news for Republicans — their problem is national, not regional.