A proposed constitutional amendment banning gay marriage takes center stage in the Senate this week, a measure even supporters say has a slim chance of success but which they hope will strike a chord with the electorate.

The Senate resumes debate on the measure Monday and is likely to vote on Wednesday. A two-thirds majority is needed to approve a change in the Constitution (search).

"We didn't expect to get two-thirds when we started out," Sen. Wayne Allard (search), the Colorado Republican who is one of the measure's chief sponsors in the Senate, told FOX News on Monday.

"We felt we needed to get pushing this right away because of what's happening with activist courts around the country and particularly in Massachusetts," Allard said referring to the first state in the nation to legalize marriages between members of the same sex.

The amendment aims to settle conflicts in state legislatures and courts over gay marriage by adding language to the Constitution that states, "Marriage in the United States shall consist only of the union of a man and a woman."

Leading the chorus of support for an amendment, President Bush (search) said in his radio address Saturday that legalizing gay marriage would redefine the most fundamental institution of civilization.

"If courts create their own arbitrary definition of marriage as a mere legal contract and cut marriage off from its cultural, religious and natural roots then the meaning of marriage is lost and the institution is weakened," he said.

Senate Majority Leader Bill Frist, R-Tenn., told reporters Monday that the amendment was needed to protect the American family.

"Marriage and family stand as the bedrock in our society. Children do best with a mom and a dad or a man and a woman," Frist said.

But as debate opened on Capitol Hill Friday, Sen. Patrick Leahy, D-Vt., said Republicans were using the constitutional amendment as a bulletin board for campaign sloganeering.

"Somehow we should find a way to restrain the impulse of some to politicize the Constitution," he said.

Sen. Orrin Hatch, R-Utah, said it was a "phony argument" to accuse the GOP of bringing the issue to a vote to make an election-year statement. Hatch then accused Democratic presidential candidate John Kerry (search) of holding inconsistent positions on marriage.

"This is the grand flip-flop; one of the grandest of all times," he said. "A person's head starts to spin trying to undo the logical mess."

Kerry and his running mate John Edwards oppose gay marriage but support civil unions. Both oppose a constitutional amendment.

Edwards' Republican rival, Vice President Dick Cheney, has also voiced support this year for the proposed constitutional amendment, putting him at odds with his wife.

Lynne Cheney said Sunday that states should have the final say over the legal status of personal relationships.

The Cheneys have two daughters -- one of whom is a lesbian -- who work in their father's campaign. The Cheney's gay daughter, Mary, is director of vice presidential operations for the Bush-Cheney re-election campaign. She held a public role as her father's assistant in the 2000 campaign and helped the GOP recruit gay voters during the 2002 midterm elections.

She has been less visible this year while traveling with the vice president or working at campaign headquarters in Arlington, Va. As the election nears, she will play a more public role, campaign aides say.

The vote puts some legislators in a difficult position. One senator acknowledged the political risk in trying to walk a line supporting both traditional marriage and gay rights.

"I intend to be your champion on many issues in the future, if you want me," Sen. Gordon Smith, R-Ore., said Friday in remarks directed at gay and lesbian voters. Smith is a leader in efforts to make attacks against homosexuals a federal hate crime.

Sen. John Cornyn, R-Texas, said voters will see the issue more starkly.

"I think a yes vote ... will be a vote in favor of traditional marriage, and a no vote or 'I didn't care enough to show up' vote will be perceived as against traditional marriage," he said.

Democrats signaled they will not throw hurdles in front of the resolution.

"We are ready to rock and roll on the debate on this," said Sen. Harry Reid, D-Nev.

The Associated Press contributed to this report.