BOB ABERNETHY, anchor: New York's highest court this week heard oral arguments about whether that state should legalize gay marriage. Similar cases are pending in the supreme courts of Washington State and New Jersey. Meanwhile, this coming week the U.S. Senate is scheduled to begin debating an amendment to the Constitution that would ban gay marriage. Most observers don't expect the measure to be approved, but there's been a flurry of faith-based lobbying nonetheless, and charges of election-year politicking. Kim Lawton reports.

KIM LAWTON: Flanked by religious leaders at the U.S. Capitol, Senate Majority Leader Bill Frist said a constitutional amendment is needed to protect traditional marriage.

Senator BILL FRIST (R-TN) (Senate Majority Leader) (Speaking at Press Conference): Marriage is the cornerstone of our society. The institution, really more than any other, determines the well-being of our future, of our children, of our communities.

LAWTON: The proposed amendment says marriage should "consist only of the union of a man and a woman" and that neither the U.S. Constitution nor any state constitution can require recognition of any other kind of marriage. After the Massachusetts highest court cleared the way for gay marriages in 2003, conservatives began pushing for this amendment.

PETER SPRIGG (Family Research Council): What we seem to be headed for is a situation in which the Constitution will be amended one way or the other on the issue of marriage. It will either be amended by the people through the democratic process, or it will be amended by activist judges who interpret the Constitution to require same-sex marriage be legalized nationwide.

Rev. HARRY JACKSON (High Impact Leadership Coalition) (Praying): We thank you in advance, Lord, though the battle is raging, that we have the victory in Jesus' mighty name.

LAWTON: A broad religious coalition has been aggressively lobbying in favor of the amendment. Outside Washington, DC, megachurch pastor Harry Jackson mobilized African-American pastors.

Rev. JACKSON (Speaking at Event): You've already got the tools in your hand to change the country. What's needed now is the courage to stand up, the courage to speak.

LAWTON: More than 50 national religious leaders, including eight Roman Catholic cardinals, released a statement urging the Senate to pass the amendment. The Knights of Columbus has distributed millions of postcards to Catholic parishes. The Southern Baptist Convention proclaimed June 4 Marriage Protection Sunday, while the Church of Jesus Christ of Latter-Day Saints asked that a letter of support be read out loud in all of its congregations.

But other faith-based groups are working against the measure. A coalition called Clergy for Fairness has launched an online petition signed by more than 1,600 clergy.

Reverend PAUL SIMMONS (Clergy for Fairness) (At Press Conference): Let there be no mistake about it. There is a broad and profound opposition to the proposed amendment among religious people. The thunder of the religious Right should be resisted as misguided and prejudicial.