HARRISBURG -- The Senate Judiciary Committee held round one yesterday on a controversial amendment to the state constitution intended to stop men from marrying other men and women from marrying other women in the Keystone State.

The judiciary panel is due to hold round two today, when it's expected to vote on whether to send the so-called Pennsylvania Marriage Protection Act to the full Senate for action.

The measure, introduced by several conservative Republican senators, led by freshman Michael Brubaker of Lancaster, is intended to bolster a 1996 state law, the Defense of Marriage Act, which already outlaws marriage between people of the same sex.

Mr. Brubaker said merely having a law on the books isn't enough, and he wants to amend the state constitution. Supporters say a future General Assembly could repeal the 1996 act, or a judge could throw it out should a gay couple bring a legal challenge to it.

Maggie Gallagher of the Institute for Marriage and Public Policy, and Janice Hollis, senior pastor of Progressive Believers Ministries in Philadelphia, supported the proposed constitutional amendment.

"There cannot be a healthy community without healthy families,'' said Ms. Hollis. "The church has a responsibility to be proactively involved in issues dealing with the family and society.''

Ms. Gallagher said about two-thirds of Pennsylvanians support traditional marriage. "They are not hate-filled bigots,'' she said. The vast majority of the standing room-only crowd of 125 people applauded her.

Supporters said Pennsylvania wouldn't be breaking new ground, since 27 other states have already changed their constitutions to define marriage as only between one man and one woman.

The Pennsylvania Catholic Conference also supported the amendment, but Pennsylvania NOW, the American Civil Liberties Union, several law professors and the Rev. Julian Hall of United Church of Christ in Hanover opposed it.

"The General Assembly has far more pressing business ... than initiating the costly and time-consuming process of amending the Pennsylvania Constitution,'' said University of Pittsburgh Law School professor Anthony Infanti.

Also opposed was Stacey Sobel of Equality Advocates of Pennsylvania. She said it would hurt nontraditional families, where two women or two men are raising a child. "It wouldn't protect'' such families, she said. "This amendment could deprive these families of necessary legal protections.''

Sen. Jane Earll, R-Erie, broke with her Republican colleagues and opposed the constitutional amendment. She called it "a dangerous precedent'' that was based on fears of "a ghost in the corner.''

She said defining marriage as one man and one woman is both already in law and in the state's domestic relations code, which she said is enough.

Even if the bill is approved by the Legislature this year, it would have to be approved again in 2009 and then put on a statewide referendum in November 2009 before the constitution would be changed.