In a little over a week after the flamboyant new mayor of San Francisco opened the matrimonial floodgates, the city issued marriage licenses to more than 3,000 same-sex couples, igniting national controversy. The move, however, was a largely a stunt. State voters in 2000 overwhelmingly passed the Defense of Marriage Act (DOMA), declaring that "only marriage between a man and a woman is valid or recognized in California."

But the provocations of Mayor Gavin Newsom pale in comparison to those of George W. Bush, who on Tuesday said he would endorse an amendment to the U.S. Constitution--only the 18th since the Bill of Rights in 1791--that places a national ban on gay marriage, and probably civil unions as well, thus superseding state authority.

Why back an amendment? Pure politics--of the most dangerous and cynical variety. Bush's advisors want him to change the subject and launch his re-election campaign on an issue that will distract attention from attacks on his credibility.

In practical terms, a constitutional amendment is utterly unnecessary. Gay marriage is no threat, and the President and his advisors know it.

So far, 38 states have passed DOMAs like California's. And a federal DOMA, signed into law by Bill Clinton in 1996, says that the U.S. government does not recognize gay marriage and that no state has to recognize gay couples even if they are legally married in another state.

Yes, the Supreme Court might some day rule that the "full faith and credit clause" of the Constitution requires all states to recognize gay couples (for bereavement rights, insurance, etc.) married in a state where gay marriage is legal. But chances of such a ruling are slim and far into the future.

The reason for Bush's endorsement is not legal, but electoral. He wants to throw red meat in the direction of radical religionists, who have made the issue their number-one priority.

Top Republican strategists believe one reason Bush nearly lost in 2000 was that fundamentalists did not turn out in large numbers. The way to energize them, says the Rev. Lou Sheldon, who heads the Coalition for Traditional Values, is for the President to lead in "protecting marriage from homosexual activism."

But, by supporting the FMA, the President is turning his back on conservative principles of federalism and limited government. Gay marriage arouses hot emotions on both sides. But there is a sensible solution, and it's being followed: Let each state decide on its own.

That is the view of Vice President Cheney. "Different states are likely to come to different conclusions," he said during the 2000 campaign, "and that's appropriate." (No state has legalized gay marriage, and Americans oppose it, 65 percent to 31 percent.) Many staunch Republicans agree with Cheney's approach. "I hold the Constitution in highest regard and I don't like to see it trifled with," says former Rep. Bob Barr. "I'm a firm believer in federalism. Even though I'm not an advocate for same-sex marriage, I want the states to decide the issue."
If the President is hunting for amendments, he might try one limiting federal spending or establishing a clear line of succession for Congress and the executive branch if terrorists set off a nuclear bomb on the Mall.

Andrew Sullivan, the popular blogger, claims that Bush has become "nanny in-chief." I wouldn't go that far, but his expansion of federal power over education and vast new spending on Medicare trouble believers in smaller government. So would his support of the FMA.

Why stoop to conquer? Bush is strong enough to win re-election on the real issues: leadership, the economy and the war. Even if he were in serious jeopardy, he should resist the red-meat route. He's not a bigot or a fanatic, so why pretend to be one? In 2004, this divided country needs a compassionate conservative, not a cynic who panders to the meanest instincts.

James K. Glassman is a fellow at the American Enterprise Institute.