DENVER (AP) -- A political generation ago, the West signaled the nation's rightward swing, from the emergence of Ronald Reagan to the success of tax-limitation ballot measures in California and Colorado.
Now, however, the fabled expanse of deserts, jagged peaks, and emerald coastlines is trending in a different direction.
The West has become largely Democratic terrain.
Voters in Washington state in November legalized marijuana and upheld the legality of gay marriage. New Mexico was once a tightly contested state, but Republicans ceded it to Democrats in the presidential campaign.
There are, as always, exceptions.
Lightly populated Idaho and Wyoming remain strongly Republican, as does Utah. Democrats are struggling in Arizona, where the 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 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 in a region already imbued with a libertarian spirit is the result of several factors. One is the growing number of people who are seeking a better quality of life by moving from more liberal states. Also, the expanding immigrant population is turned off by increasingly hard-line Republican immigration proposals.
"Look at the migration patterns," said Sig Rogich, a Republican consultant in Las Vegas who worked on Reagan's presidential campaigns. "You're seeing the aftermath of a new generation of young men and women whose parents moved westward."
Western states generally have weak political parties, part of the legacy of their political maturation during the progressive era at the start of the 20th century. Most local elections are nonpartisan affairs and voters often have the right to set policy unilaterally via ballot initiative. Western voters long have cherished nonpartisan independence, even when they voted a relatively straight party ticket.
"The West is the most American part of America," said Dave Kopel of the Independence Institute, a libertarian think tank in Denver. "It is a place where you have much more respect for individual choice and you have more ability to be who you want to be."
During the 1980s and 1990s, that libertarian streak fed a series of Republican victories as voters approved tax-limitation initiatives, protested federal environmental rules and kept statehouses firmly in the GOP's hands. But nowadays it means something else, Carrick said.
"The libertarian thing is no longer about property rights or gun rights," he said. "It's now about letting people live their lives as they choose."
Ironically, Republicans' success may have contributed to that shift.
The party managed to enshrine staunch anti-tax measures in several states' constitutions through ballot initiatives, making it very difficult to raise taxes in California, Colorado and Washington state.
As a result, Democrats can't easily raise revenue, but they also can't be attacked for doing so, said Ron Dotzauer, a Seattle-based Democratic strategist. "They can't be defined as the pro-tax group because they can't tax," he said.
There are prominent Republicans who demonstrate that the party can still win the region.
Brian Sandoval in Nevada and Susana Martinez in New Mexico are popular Republican governors, but their relatively moderate stances often put them at odds with the national party. Both, for example, just agreed to the Medicaid expansion under President Barack Obama's health care plan, something that is anathema to many conservative Republicans.
"People appreciate a leader who takes more pragmatic approaches," said Nicole McCleskey, a New Mexico-based GOP pollster who advises Martinez.
McCleskey argued that Democrats' success in the region is overstated and she noted that, outside of California, Republicans in 2012 only lost one Western congressional seat. As an example of how Republicans can succeed, she cited New Mexico, where the party picked up seats in the Legislature despite the Obama wave.
But McCleskey acknowledged that New Mexico Republicans were helped by the national GOP basically giving up on the presidential race in the state. GOP presidential nominee Mitt Romney did not contest the state, minimizing the damage of a divisive presidential campaign.
"We were able to localize a lot of these races and build on the change that has taken place with a strong Republican governor," she said. "Republicans fought on state issues and the Democrats tried to fight on national issues."
Jill Hanauer is a Democratic strategist who engineered her party's takeover of the Colorado Legislature in 2004. She agrees with McCleskey that the West cannot be considered a Democratic lock.
"The reason Democrats or progressives are winning is that Republicans got fat and happy," said Hanauer, who is now president of Project New America, a political data and strategy company in Denver. "The worst thing that can happen for Democrats is to take it for granted."
In 2002, Ruy Teixeira, a Washington, D.C.-based Democratic strategist, co-wrote "The Emerging Democratic Majority," which predicted that demographic and social trends would turn parts of the country that were deep red, such as the interior Mountain West, into Democratic-leaning states. The book, published shortly after Republicans took back the U.S. Senate in the 2002 elections, was received skeptically.
Last year, Teixeira and other researchers published a new book on the Mountain West as America's new swing region. Now there was little pushback.
Teixeira said the West's shift has been dramatic because of the heavy migration to the region. Another factor is the ballot initiative process, which magnifies political trends by making it easier to enact dramatic policy changes such as marijuana legalization.
But he said 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.
"It's not like there's something in the water in state X that's making them harder for Republicans," Teixeira said. "It's just the same series of changes that are working themselves out in all states."