DENVER (AP) — While gays and lesbians across the country claimed victory after a June 26 Supreme Court ruling that knocked down a legal prohibition of gay sex, freshman Republican Rep. Marilyn Musgrave insists the real battle is over the right of gays to marry.

And she is leading a charge to make sure that doesn’t happen.

The mother of four from the plains of northeast Colorado has introduced a proposed constitutional amendment that would effectively outlaw gay marriage. The bill has 25 co-sponsors and the endorsement of Senate Majority Leader Bill Frist.

“I am firmly committed to keeping marriage as it is now, between a woman and man,” Musgrave said in a telephone interview.

Musgrave’s proposal, offered May 21, has been referred to the House Judiciary subcommittee on the Constitution. It says: “Marriage in the United States shall consist only of the union of a man and a woman. Neither this Constitution nor the constitution of any state under state or federal law shall be construed to require that marital status or the legal incidents thereof be conferred upon unmarried couples or groups.”

To be added to the Constitution, the proposal must be approved by two-thirds of the House and the Senate and ratified by three-fourths of the states.

Gov. Bill Owens said Colorado was not affected by the Supreme Court ruling and noted the state already has a law banning gay marriage. State GOP Chair Ted Halaby said he had not heard of Musgrave’s bill.

During her eight years in the Colorado Legislature, Musgrave co-sponsored a successful 2000 bill that defined a marriage as a union between one man and one woman.

She also pressed for legislation expanding the right to carry concealed weapons and requiring doctors to provide brochures and a videotape to women seeking abortions. The video would include a fetal heartbeat.

Musgrave cited the U.S. Supreme Court’s decision and the possibility of a similar ruling by the Supreme Court of Massachusetts as reasons for proposing the amendment.

“Homosexual activists are wanting to go to unelected judges to get their way rather than going through the legislative process and allowing the people to decide,” she said.

Some recent polls have suggested opposition to gay marriage is slipping.

Rick Cendo, who plans to travel to Canada to marry his partner, Gary Hamner, said Musgrave and others underestimate the commitment of gays to their partners.

“I’ve been with Gary for 11 years. That is not a bad record,” he said. “What are we going to do that is going to hurt marriage? I am as much a part of this civilization as anyone else. I don’t want it to go under.”

Winnie Stachelberg, political director of the Human Rights Campaign, said the Constitution has traditionally been used to expand rights. She said critics should spell out how gay unions will undermine the institution of marriage.

“This isn’t about forcing churches and synagogues to perform marriages,” she said. “It is about civil marriages. Marriage is a contract.”