Fifteen years ago, in his first book, Dead Right, David Frum identified several challenges facing Republicans. He cited the “fundamental contradiction” of William Weld, at the time governor of Massachusetts, who thought he could be a fiscal conservative and a social liberal. Frum recounted how this Republican blue-blood, unable to reconcile the two positions, evolved into a thoroughgoing liberal who pushed through huge budget increases, in much the same way that John Stuart Mill, who objected to the social conservatism of his day, ended up a socialist.

Had this disconnect been limited to one governor in one state, Frum’s point might have become an historical footnote. Yet from Christine Todd Whitman of New Jersey to Arnold Schwarzenegger of California — not to mention political operatives like John McCain’s campaign manager, Steve Schmidt — influential voices continue to maintain that the Weld synthesis not only is plausible but also holds electoral promise. These Republicans resent the presence of social conservatives in the party and, even more, the fact that in 30 states social conservatives have succeeded in defending the legal status of matrimony against elites who want America to be more like socially liberal Europe.

Even many Republicans with no beef against social conservatives don’t consider marriage a winning issue. But as Maggie Gallagher pointed out recently in National Review (August 10), public support for the traditional legal definition of marriage remains strong, and indeed has increased — to nearly 60 percent — since Perez Hilton heaped public scorn on beauty queen Carrie Prejean in April.

So why aren’t the geniuses at the Republican National Committee taking advantage of this issue, in Gallagher’s words, “to elect our friends and defeat our enemies”? The Democrats surely understand the game, yet Michael Steele has remained silent on the marriage battles taking place in various states this year. Nor has he sought any photo-op to demonstrate solidarity with African-American clergymen who are behind the effort to allow the voters — and not the city council — to determine the legal definition of marriage in the District of Columbia.

What drives the shortsightedness is that far too many in the GOP — from the business crowd to the Washington insiders, from the conservative think tanks to the talking heads on Fox News — have been slow to learn that social conservatism and economic conservatism are joined at the hip. Without the social ideal of marriage between husband and wife, described by Wendell Berry as “the fundamental connection without which nothing holds,” the prospects for limited government, civil society independent of the state, and a robust, free-market economy go out the window.

As we can see from what has happened in Old Europe, state creation of same-sex marriage has seriously undermined marriage as a social institution. Data from the World Values Survey and the International Social Survey Programme show that countries with same-sex marriage demonstrate the lowest levels of support for traditional marriage. Citizens in these countries are significantly less likely than their counterparts in the U.S. and Australia to agree that adults who desire children should wed; they are significantly more likely to approve of cohabitation without marital intentions and to consider divorce to be the best solution to marital problems.

According to NRO contributor Stanley Kurtz, marriage, and especially married parenthood, are disappearing in Denmark, Sweden, and Norway, countries that adopted same-sex marriage between 1989 and 1994. Kurtz says this “culture-shifting event” has pushed rates of unwed childbearing over the top in Scandinavia. Today, births to unwed mothers exceed 55 percent of total births in Sweden and 50 percent in Norway. In Denmark, more than 60 percent of first-born children have unwed parents.

Europe’s dismissal of the social ideal of traditional marriage comes right out of the Marxist playbook. Karl Marx considered matrimony to be as evil as private property, and he called for “the abolition of the family” in a post-capitalist society, with children being raised communally rather than by their married mothers and fathers.

If the Left understands the relation between the family order and the economic order, why don’t Republicans? Even language affirms the connection: The term economy originates from a Greek word, oikos, which means household. Adam Smith noted the interplay between marriage and the market in The Wealth of Nations. Like Alexis de Tocqueville in 1835, the Scottish moral philosopher was impressed with what he saw in America in 1776. He noticed how men and women on this side of the Atlantic were twice as likely to marry — and at younger ages — and had twice as many children as their European counterparts.