Can it be? One of the oddest paradoxes of modern cultural politics may at last be resolved.

The paradox is this: Cultural conservatives revel in condemning the loose moral values and louche lifestyles of "San Francisco liberals." But if you want to find two-parent families with stable marriages and coddled kids, your best bet is to bypass Sarah Palin country and go to Nancy Pelosi territory: the liberal, bicoastal, predominantly Democratic places that cultural conservatives love to hate.

The country's lowest divorce rate belongs to none other than Massachusetts, the original home of same-sex marriage. Palinites might wish that Massachusetts's enviable marital stability were an anomaly, but it is not. The pattern is robust. States that voted for the Democratic presidential candidate in both 2004 and 2008 boast lower average rates of divorce and teenage childbirth than do states that voted for the Republican in both elections. (That is using family data for 2006 and 2007, the latest available.)

You can do a good job of predicting how a state will vote in national elections by looking at its population's average age at first marriage and childbirth.

Six of the seven states with the lowest divorce rates in 2007, and all seven with the lowest teen birthrates in 2006, voted blue in both elections. Six of the seven states with the highest divorce rates in 2007, and five of the seven with the highest teen birthrates, voted red. It's as if family strictures undermine family structures.

Naomi Cahn and June Carbone -- family law professors at George Washington University and the University of Missouri (Kansas City), respectively -- suggest that the apparent paradox is no paradox at all. Rather, it is the natural consequence of a cultural divide that has opened wide over the past few decades and shows no sign of closing. To define the divide in a sentence: In red America, families form adults; in blue America, adults form families.

Cahn and Carbone's important new book, Red Families v. Blue Families: Legal Polarization and the Creation of Culture, from Oxford University Press, is too rich with nuance to be encompassed in a short space. But here is the gist.

For generations, American family life was premised on two facts. First, sex makes babies. Second, low-skilled men, if they apply themselves, can expect to get a job, make a living, and support a family.

Fact 1 gave rise to a strong linkage between sexual activity, marriage, and procreation. It was (and still is) difficult for teenagers and young adults to abstain from sex, so one important norm was not to have sex before marriage. If you did have premarital sex and conceived a child, you had to marry.

Under those rules, families formed early, whether by choice or at the point of a shotgun. That was all right, however, because (Fact 2) the man could get a job and support the family, so the woman could probably stay home and raise the kids. Neither member of the couple had to have an extended education in order to succeed as spouse or parent.

True, young people often make poor marital choices. But that, too, was usually all right, at least from society's point of view, because divorce was stigmatized and fairly hard to get. Even a flawed marriage was likely to be a stable one. Over time, the spouses would grow into their responsibilities.

That is what "families form adults" means. Many teenagers and young adults formed families before they reached maturity and then came to maturity precisely by shouldering family responsibilities. Immature choices and what were once euphemistically called "accidents" were a fact of life, but the unity of sex, marriage, and procreation, combined with the pressure not to divorce, turned childish errors into adult vocations.

But then along come two game-changers: the global information economy and the birth-control revolution. The postindustrial economy puts a premium on skill and cognitive ability. A high school education or less no longer offers very good prospects. Blue-collar wages fall, so a factory job no longer cuts it -- if, that is, you can even find a factory job.

Meanwhile, birth control separates decisions about sex from decisions about parenthood, and the advent of effective female contraception lets men shift the moral responsibility for pregnancy to women, eroding the shotgun marriage. Divorce becomes easy to obtain and sheds its stigma. Women stream into the workforce and become more economically independent -- a good thing, but with the side effect of contributing to a much higher divorce rate.

In this very different world, early family formation is often a calamity. It short-circuits skill acquisition by knocking one or both parents out of school. It carries a high penalty for immature marital judgment in the form of likely divorce. It leaves many young mothers, now bearing both the children and the cultural responsibility for pregnancy, without the option of ever marrying at all.

New norms arise for this environment, norms geared to prevent premature family formation. The new paradigm prizes responsible childbearing and child-rearing far above the traditional linkage of sex, marriage, and procreation. Instead of emphasizing abstinence until marriage, it enjoins: Don't form a family until after you have finished your education and are equipped for responsibility. In other words, adults form families. Family life marks the end of the transition to adulthood, not the beginning.

Red America still prefers the traditional model. In 2008, when news emerged that the 17-year-old daughter of the Republican vice presidential nominee was pregnant, traditionalists were reassured rather than outraged, because Bristol Palin followed the time-honored rules by announcing she would marry the father. They were kids, to be sure, but they would form a family and grow up together, as so many before them had done. Blue America, by contrast, was censorious. Bristol had committed the unforgivable sin of starting a family too young. If red and blue America seemed to be talking past one another about family values, it's because they were.

When you understand all of that, you also understand why you can do a good job of predicting how a state will vote in national elections by looking at its population's average age at first marriage and childbirth. In 2007, for example, the states with the lowest median age at marriage in 2007 were all red (Arkansas, Idaho, Kansas, Oklahoma, and Utah). The states with the highest first-marriage age were all blue (Connecticut, Massachusetts, New Jersey, New York, and Rhode Island). The same pattern holds for age at first childbirth. Massachusetts is highest (about 28 years old), Mississippi lowest (about 23 years old).

A further twist makes the story more interesting, and more sobering. Cahn and Carbone find an asymmetry. Blue norms are well adapted to the Information Age. They encourage late family formation and advanced education. They produce prosperous parents with graduate degrees, low divorce rates, and one or two over-protected children.

Red norms, on the other hand, create a quandary. They shun abortion (which is blue America's ultimate weapon against premature parenthood) and emphasize abstinence over contraception. But deferring sex in today's cultural environment, with its wide acceptance of premarital sex, is hard. Deferring sex and marriage until you get a college or graduate degree -- until age 23 or 25 or beyond -- is harder still. "Even the most devout overwhelmingly do not abstain until marriage," Cahn and Carbone write.

In any case, for a lot of people, a graduate education or even a bachelor's degree is unrealistic. The injunction to delay family formation until you are 24 and finish your master's offers these people only cold comfort.

The result of this red quandary, Cahn and Carbone argue, is a self-defeating backlash. Moral traditionalism fails to prevent premarital sex and early childbirth. Births precipitate more early marriages and unwed parenthood. That, in turn, increases family breakdown while reducing education and earnings.

"The consequential sense of failure increases the demands to constrain the popular culture -- and blue family practices such as contraception and abortion -- that undermines parental efforts to instill the right moral values in children," Cahn and Carbone say. "More sex prompts more sermons and more emphasis on abstinence." The cycle repeats. Culturally, economically, and politically, blue and red families drift further apart as their fortunes diverge.

Whether Cahn and Carbone are right will take time and subsequent scholarship to learn; but their story is both plausible and sobering. Plausible, because it brings so many aspects of the culture wars into sharper focus. Sobering, because the economic and cultural forces battering traditional family norms show no signs of abating -- but the new, education-centered pathway to adulthood is often least accessible to those who need it most.