The bullet trains that would someday streak through California at 220 mph are, in the vision of their most ardent supporters, more than just a transportation system. They are also a means to alter the state's social, residential and economic fabric.
But those broader ambitions are triggering an increasingly strident ideological backlash to the massive project.
The fast trains connecting Los Angeles and San Francisco would create new communities of high-density apartments and small homes around stations, reducing the suburbanization of California, rail advocates say. That new lifestyle would mean fewer cars and less gasoline consumption, lowering California's contribution to global warming.
The rail system also would reduce the economic and transportation isolation of the Central Valley, which would grow by 10 million or even 20 million people, according to Gov. Jerry Brown.
"We are going to have to live closer together" and accommodate growth in more environmentally sustainable ways, Brown said in a recent interview. "The high-speed rail will be built in that vein."
Opponents, most of whom are political conservatives, regard the ambitious project as a classic government overreach that will require taxpayer subsidies. But they also see something more sinister: an agenda to push people into European or Asian models of dense cities, tight apartments and reliance on state-provided transportation.
In their view, the rationale of the rail system rests on flawed assumptions that would undermine California's identity, which during the last half-century has revolved around single-family homes that have driven economic growth, family-oriented lifestyles and signature West Coast recreation.
"It is a real movement in California of controlling the masses, controlling land use, deciding where people should live," said Rep. Devin Nunes (R-Tulare). "I oppose that absolutely, because it is a form of left-wing social engineering."
When voters approved funding for the rail system in 2008, it was promoted as nonpartisan. Even some Republicans supported it. But the $98.5-billion project has taken on powerful political and philosophical overtones as it has matured. It now reflects much broader conflicts about the state's future, government spending and, most important, efforts to change the way people live.
Whether California's classic style of growth, which created population clusters in the San Fernando Valley, Orange County and the Inland Empire, is sustainable is a matter of sharp political debate. But the justification for high-speed rail depends on something even more basic: projections that the state's population will continue growing rapidly.
The California High-Speed Rail Authority's business plan for the project asserts that the state will have 60 million people by 2050, up from the current 37.3 million, with most of the growth in the agricultural heartland.
The project "is based on an optimistic assessment of where California is going," Brown said after the plan was released.
Academic experts say the growth models that put the state's population at 60 million by mid-century lack credibility. And the state Department of Finance is now revising official population projections downward.
Walter Schwarm, a state demographer, said the lower estimates are based on three factors: California overestimated its population before the 2010 census; as many people will move out of the state in the future as move in; and Latino birthrates are declining.
"We have always assumed in the past that we were a strong magnet for individuals, but now we are looking like every other state. People move in and people move out," Schwarm said.
The state's economic outlook also raises questions about whether it can support a bigger population, particularly in the Central Valley, racked by some of the highest unemployment in the nation.
"What are all of these 10 million additional people going to be doing for a living in the Central Valley?" asks USC historian and author Kevin Starr. "You have to ask are these going to be 10 million more taxpayers or 10 million people who have to be supported by other taxpayers?"
Starr has written that the state's boom after World War II revolved around single-family homes, an outcome that "had its psychological origins in the deepest recesses of American identity." It led, he said in his book "California Dreams," to "a tidal wave of marriage, sexuality, procreation and family building." The bullet train is supposed to help rewrite that blueprint.
The rail authority paid Calthorpe Associates, a Berkeley-based urban planning company, $1.6 million for a report, "Vision California: Charting Our Future," which laid out the case for compact communities reducing demand for residential land, single-family homes, vehicles, energy and water.
Company principal Peter Calthorpe said in a New York City speech in November that high-speed rail is more than a technology to move people.
"It is the thing that lays the groundwork for the kinds of communities that are possible," he said. "It is not just the cost of high-speed rail versus the alternative highways and airports. It is the cost difference between two different lifestyles that inevitably emerge."
Calthorpe's ideas are anathema to conservatives.
"It has nothing to do with transportation. This is entirely social policy," said Rep. Tom McClintock (R-Granite Bay). "It is all about the far left's fever dream to get mother Earth back to a pristine condition by elbowing us into these dense urban cores."
Calthorpe said conservatives mischaracterize his ideas. "They turn it around, like Republicans always do, and say we want to force everybody into apartments."
One exception is Transportation Secretary Ray LaHood, the lone Republican in the Obama Cabinet, who disagrees with rail opponents in his party. "They are not in sync with the people they represent. I am a Republican and I am leading the charge on high-speed rail and proud of it."
Leaders in the home building and agriculture industries remain skeptical.
Mike Winn, president of the California Building Industry Assn., said his members believe that at least half of future home buyers will want detached family homes, not the 30% that some government agencies project.
"This has been developed and designed as a suburban state," Winn said. "It won't change in one generation. Sure, you can bemoan the long commutes, but you are not going to undo the cultural allure of living in a single-family home."
The rail authority also argues that the bullet train will preserve farmland by concentrating growth in city centers. It's a laudable goal, but not a believable one, said Chris Scheuring, an environmental attorney at the California Farm Bureau Federation.
High-speed rail "directly and immediately eats up farmland," he said. "The beneficiaries are urban and the people holding the bag are rural. My guys are looking at this as a real loser for agriculture."
The argument that the rail line would concentrate population in the cities is "just a hypothesis. The counties are still going to be seduced by highways and commercial development."
Even the argument that the rail system would reduce greenhouse gases — the rail authority claims savings of 3 billion pounds of carbon dioxide annually — is questioned.
Robert Poole, a transportation specialist at the libertarian Reason Foundation, said the Obama administration's push to improve automobile fuel efficiency would cause a significant drop in carbon dioxide emissions, apart from the rail project.
In addition, building hundreds of miles of bullet train bridges and tunnels is so carbon-intensive it would take decades for the system to break even on greenhouse gas emissions.
A 2010 UC Berkeley study asserted that the rail system, based on the median estimate of riders, would take 71 years to break even in greenhouse gas emissions. Mikhail Chester, an author of the study, said adjustments for cleaner electricity generation and other factors in the future could yield a net reduction in greenhouse gases in 30 years.
That's still a costly trade-off for Poole. "It is like using an atomic bomb to kill a housefly," he said.
The sharply divergent views of high-speed rail reflect larger divisions in charting the state's future, Starr said.
"The arguments for and against the train go right to the core of the unresolved nature of politics in California," he said.