Marriage is a hot topic these days, especially in light of President Bush's call for a constitutional amendment to define the very concept.

It's good to see attention focused on marriage, because this vital institution has been weakened in recent decades. Today, one child in three is born outside of marriage. And a large portion of kids born to married couples will see their parents divorce before their 18th birthday.

The erosion of marriage is bad news for children and society. Marital decline is the leading cause of child poverty and welfare dependence in our nation. Almost two-thirds of poor children live in single-parent homes. Three-quarters of all welfare expenditures for children -- at a cost of $150 billion per year -- go to single parents. Children raised without a father in the home are substantially more likely to suffer emotional problems, fail in school, do drugs, commit crimes, and end up on welfare as adults.

Clearly, dads and wedding rings are good for kids. But, ironically, the current welfare system penalizes couples who marry and rewards moms for staying single.

Recognizing the value of marriage to children and adults, President Bush has proposed a new "healthy marriage initiative." The Senate will consider the president's plan as part of welfare reform legislation later this month.

The cost of the president's proposal is modest, only one penny to promote healthy marriage for every $5 government currently spends subsidizing single parents. Still, that small investment can pay large dividends down the road. By fostering better life decisions and stronger relationship skills, marriage-promotion programs can increase child well being and adult happiness. They also can reduce child poverty and welfare dependence.

All participation in the marriage program would be voluntary. The program would provide training in relationship skills to low-income couples interested in marrying. It also would experiment with reducing the anti-marriage penalties in welfare.

The program would teach relationship skills to unmarried couples before they have children, with a focus on delaying pregnancy until a couple has made a commitment to healthy marriage. It also would intervene at the "magic moment" of a child's birth, when both father and mother are most open to marrying.

Surveys show that about 75 percent of non-married expectant mothers are romantically involved with their child's father at or around the time of the child's birth. Most of these young adult couples express positive attitudes about marriage and say they hope to marry in the future. Yet relatively few will, in fact, marry. Most split up a few years after the child's birth.

But the marriage program would offer these low-income couples a better chance at the future. By teaching couples how to deal with relationship problems, the program will increase their odds of marrying and staying together.

If we can help even some of these couples build happy marriages, we'll end up saving far more in welfare payments than we'll have invested in marriage training.

Still, opponents are doing everything they can to derail the president's initiative.

Former Labor Secretary Robert Reich claims the plan wouldn't work because there aren't enough "marriage-worthy men" in low-income communities.

Not true. As noted, nearly three-quarters of non-married mothers are cohabiting or romantically involved with their children's fathers at the time of the birth. The median income of these non-married fathers is $17,500. Some 70 percent of poor single mothers would be lifted out of poverty if they simply married the fathers of their children.

Other critics charge the program would increase domestic violence by encouraging women to remain in dangerous relationships.

Yet studies show marriage-skills training reduces domestic violence, by helping women avoid dangerous and counterproductive relationships. And in general, domestic violence is more common in cohabiting relationships than in marriage: Never-married mothers, for example, are twice as likely to experience domestic violence than are mothers who have married.

Marriage benefits everyone. The social-science research shows that married adults are happier and more productive on the job, earn more, enjoy better physical and mental health, and outlive their unmarried peers.

It's an institution worth preserving -- and promoting.

Melissa Pardue is a policy analyst and Robert Rector is a senior research fellow in domestic policy at The Heritage Foundation.