WASHINGTON — The Senate Judiciary Committee began emotional hearings Wednesday on a proposed constitutional amendment to ban same-sex marriage — seen either as a last stand for traditional family values or an attempt to rob gays of civil rights.

The session made for unusual alliances. Some liberals supported the amendment plan, others hated it. Likewise some conservatives praised it, and others abhorred it. Ditto for Democrats. And for Republicans. And for African-American leaders. And church groups.

Among leaders of the chorus praising the proposed amendment is Sen. Orrin Hatch, R-Utah, the committee chairman — although he also says alternatives besides a constitutional amendment should be considered too.

"It is now clearer to me than ever that courts are usurping the role of legislatures by imposing their own definitions of marriage on the people, and we must do something about this," Hatch said in a written statement. "I think we need to consider amending the Constitution" — and said he would vote for a version favored by President Bush.

The hearing comes as the highest court in Massachusetts ruled that state must allow gay marriage — and as local officials in California, New York, New Mexico and Oregon have begun allowing them. Last week, Bush called for a constitutional amendment to define marriage as between a man and a woman.

As couples — of both the married and same-sex variety — crowded the hearing room with their children to serve as symbols of what is at stake, both sides made their arguments before the Judiciary Subcommittee on the Constitution.

NAACP President Hilary Shelton opposed the proposed amendment, saying it would "discriminate and restrict rather than expand and protect the rights for any and all persons."

But the Rev. Richard Richardson of the Black Ministerial Alliance of Greater Boston said, "As an African-American, I know something about discrimination. . . . The traditional institution of marriage is not discrimination. And I find it offensive to call it that."

Richardson said traditional marriage is the best institution to ensure that children are raised by a loving mother and father. He said that ideal is under attack on many fronts and that disintegrating families have dire consequences in inner cities he serves. "Without traditional marriage, it is hard to see how our community will be able to thrive."