Though the U.S. Senate defeated the Federal Marriage Amendment (FMA) on Wednesday, this battle is far from over. Some traditional, pro-family groups remain sure that gay marriage is a watershed contest, and they retain powerful allies in the White House and Congress. On the other side, gay-rights supporters have shown a remarkable ability to advance their agenda rapidly. No matter the fate of this particular legislation, they will continue to agitate for society's blessing.

Thus far, however, the FMA debate has lacked historical perspective. Discussion about the likelihood of the amendment's passage, not to mention the implications of its success, has been largely missing while partisans spin the political consequences. But one period from American history illustrates both the promise of Christian politicking and peril of legislating morality—Prohibition.

America's founding fathers deliberately crafted the Constitution to make amending it difficult. Overwhelming public support is needed to meet the requirements of two-thirds votes in both houses of Congress and approval from three-fourths of the nation's state legislatures. It is no coincidence, then, that spectacular events are often needed to launch the amendment process. The first 10 amendments—our Bill of Rights—were ratified to ensure the Constitution's very existence. Indeed, not until the Civil War could the Constitution be amended to grant non-whites the right to live free, attain equal protection under the law, and vote.

So consider the widespread popularity of Prohibition. No dramatic event was needed to ban the manufacture or sale of any drink containing more than .05 percent alcohol. Sure, World War I helped incite Americans ...