All right, so the Republicans have had better years. But don't forget their secret weapon. Not an ABM, MIRV, or MX. An MPA: the Marriage Protection Amendment, precision-targeted on same-sex marriage and, through it, the Republican base.

The MPA would amend the U.S. Constitution to forbid gay couples to marry. Senate Majority Leader Bill Frist, R-Tenn., says he will bring the amendment up during the week of June 5. It has zero chance of passing by the required 67-vote majority, as Frist knows. In 2004, the amendment garnered only 48 Senate votes, and the Human Rights Campaign, a gay-rights group, figures it will get only about 52 votes this year.

So why bother? Consider Virginia, where in 2004 the Republican-controlled Legislature hit on the promising formula of passing both a whopping tax increase and a gratuitously vindictive anti-gay-marriage law. (The so-called Marriage Affirmation Act outlawed not only gay marriage and civil unions, but also private contracts between same-sex individuals seeking to replicate marital arrangements.) Lyndon Johnson once said, "Hell, give [a man] somebody to look down on, and he'll empty his pockets for you." The Virginia formula was in that vein: Knock the gays hard enough, and maybe conservatives wouldn't notice the tax hike.

In Virginia, the moral-values credit card seemed to have maxed out in 2005; Democrats held the governorship. Nationally, many conservative voters seem to have noticed that the same Republican politicians who are trotting out the marriage amendment have also spent up a storm, created the biggest new entitlement program since LBJ's Great Society, riddled the budget with earmarks, and approved unprecedented restraints on political activity.

Whatever its political merits, the MPA remains as unwise substantively as when it first came up in 2004. Since then, moreover, the case for its necessity has disintegrated.

The question posed by the marriage amendment is not just whether gay marriage is a good idea, but who should decide—the states or the federal government? From its debut in 2001, the marriage amendment was misleadingly advertised as a restriction on activist courts. In truth, the amendment would strip the power to adopt same-sex marriage not only from judges but from all 50 states' legislators, governors, and electorates.

Defining and regulating marriage has been within states' purview since colonial times. (Utah was required to ban polygamy while it was still a federal territory. On the few occasions when the U.S. Supreme Court has intervened, it has curtailed states' powers to restrict marriage rights, not imposed a definition.)

Why should the federal government usurp the states' authority over marriage? Amendment supporters have insisted that gay marriage anywhere would soon spread everywhere. How, they demanded, could one state have a separate definition of marriage without creating chaos? Unless the federal government stepped in, they said, one or two states would impose same-sex marriage on all the rest.

Actually, states have defined marriage differently for most of the country's history. Until the 1960s, mixed-race marriages were recognized in some states but not others. That each state is entitled to regulate marriage in accord with its public policy views is established legal precedent; otherwise Maryland, say, could start marrying 10-year-olds and every other state would be obliged to go along—an absurdity. Moreover, in 1996 Congress passed the Defense of Marriage Act, which explicitly relieved the states of any obligation to recognize other states' same-sex marriages.

Federal-amendment proponents have claimed that the Supreme Court might strike down DOMA. That argument, already weak on the law (DOMA is almost certainly constitutional), is even weaker now that President Bush's two Supreme Court appointments, Chief Justice John Roberts and Associate Justice Samuel Alito, have solidified the Court's conservative majority. Would-be amenders are now reduced to claiming that the Constitution should be revised to pre-empt a hypothetical ruling by a future Supreme Court. On this prophylactic theory of constitutional jurisprudence, it is hard to imagine what amendment might not be in order.

So far, DOMA has stood up. The country's most liberal federal appeals court, the California-based 9th Circuit, saw off a challenge to DOMA just this month. Meanwhile, for more than two years Massachusetts has been marrying same-sex couples, including couples who travel and move outside the state. Spot the chaos? The wholesale legal confusion?

In fact, what is most remarkable about Massachusetts's gay-marriage experiment is how little legal confusion and inconvenience it has caused. As evidence that a state-by-state approach is unworkable, proponents of a federal amendment can point to a messy Virginia child-custody case and—well, not much else.

The social ramifications of gay marriage will take time to unfurl; but if rampant legal confusion were going to be the result of Massachusetts' gay marriages, it should have begun to appear by now.

Indeed, few defenders of a state-by-state approach would have dared predict that the Massachusetts experiment would create as few legal tangles as it has. That the states can go their separate ways on gay marriage is no longer a prediction; it is a fact.

MPA supporters note that a court, and not the people, ordered gay marriage in Massachusetts. That is true but not relevant. Congress has no more business overriding state courts than it does overriding state legislatures. If a state fears that its courts will order gay marriage, it can change its constitution, which is exactly what 18 states have already done and what as many as nine more will do in November. More than half the states have statutorily banned gay marriage. A handful of states—California, New Jersey, New York, and Washington are possibilities—might wind up with judicially imposed gay marriage; the large majority, it is now clear, will not.

In 2004, MPA advocates liked to say that pre-empting state legislatures and electorates was of no practical consequence, because only judges would support so alien a notion as same-sex marriage. That argument expired last September, when the California Legislature passed the Religious Freedom and Civil Marriage Protection Act, a bill legalizing same-sex marriage. Republican Gov. Arnold Schwarzenegger vetoed the bill, but the question is no longer academic: How do MPA proponents, who claim to champion democratic decision-making, justify handcuffing the democratically elected Legislature of the largest state in the union?

At bottom, what many MPA proponents want to forestall is not judicially enacted gay marriage; it is gay marriage, period. They say that an institution as fundamental as marriage needs a uniform definition: a single moral template for the whole country.

That argument would seem more compelling if marriage were more important than human life. Many of the same conservatives who want the federal government, not the states, to settle gay marriage also want the states, not the federal government, to settle abortion. Sen. George Allen, R-Va., for example, supports the MPA, but he would like to see Roe v. Wade "reinterpreted" so that states would decide the fate of abortion. Although the 2004 Republican platform calls for a "human life amendment to the Constitution," you will look in vain for any such amendment on the Senate floor.

Two questions for anti-gay-marriage, anti-abortion Republicans: If states can be allowed to go their own way in defining human life, why not allow them to go their own way in defining marriage? Where constitutional amendments are concerned, why is preventing gay couples from marrying so much more urgent than preventing unborn children from being killed?

It is precisely because marriage is so important, and because it is the subject of such profound moral disagreement, that a one-size-fits-all federal solution is the wrong approach. California and Texas, Massachusetts and Oklahoma take very different views of same-sex marriage. By localizing the most intractable moral issues, federalism prevents national culture wars.

In 2006, that argument is no longer hypothetical. Federalism is working. As the public sees that states are coping competently and that no one state will decide for all the rest, the atmosphere of panic over gay marriage has mercifully subsided, providing the time and calm that the issue needs.

The national Republican leadership's bid to upset this emerging equilibrium is demagoguery, which is sad. Conservative politicians' betrayal of federalist principles to distract attention from their broken promises is cynicism, which is sadder. And none of this is surprising -- which is saddest of all.

© Copyright 2006 National Journal

Jonathan Rauch is a senior writer and columnist for National Journal and a frequent contributor to Reason. The article was originally published by National Journal.