Short on votes and beset by internal divisions, Senate Republicans struggled Tuesday to salvage a respectable defeat for a constitutional amendment banning gay marriage (search), an issue that President Bush pushed toward the top of the election-year agenda.

"This issue is not going away," Majority Leader Bill Frist (search) of Tennessee said in a virtual concession that the measure would fall short of the 60 votes needed to advance past a Wednesday test vote. "Will it be back? Absolutely, yes," he added.

Democrats, many of whom oppose the measure, took delight in the internal Republican woes, and Sen. Dick Durbin of Illinois read aloud from a recent statement on the issue by Lynne Cheney (search), wife of the vice president. "When it comes to conferring legal status on relationships, that is a matter that should be left to the states," he quoted her as saying.

The emotionally charged proposal, backed by the president and many conservatives, provides that marriage within the United States "shall consist only of a man and a woman."

A second sentence says that neither the federal nor any state constitution "shall be construed to require that marriage or the legal incidents thereof be conferred upon any union other than the union of a man and a woman." Some critics argue that the effect of that provision would be to ban civil unions, and its inclusion in the amendment has complicated efforts by GOP leaders to gain support from wavering Republicans.

While there was no disagreement that the measure would fall short of the 60 votes needed to advance, Republicans held out hope they could gain a majority. Even that seemed in doubt, although their chances improved when an aide to Sen. John Kerry said he and vice presidential running mate John Edwards did not intend to return to the Capitol for what amounted to a procedural vote. Both men oppose the amendment.

The Senate moved toward a showdown as House Republicans pursued a different plan -- seeking to pass legislation rather than an amendment.

The House Judiciary Committee scheduled a meeting for Wednesday on a measure to strip federal courts of jurisdiction over a portion of a 1996 federal law that defined marriage as the union between a man and a woman.

Bush urged the Republican-controlled Congress last February to approve a constitutional amendment, saying it was needed to stop judges from changing the definition of the "most enduring human institution."

The odds have never favored passage in the current Congress, in part because many conservatives are hesitant to overrule state prerogatives in the area of issues such as marriage.

But Republican strategists hope to force Democrats to choose between voting the wishes of their liberal constituents, some of whom favor gay marriage, or in favor of an amendment that polls show is favored by a heavy majority of the country.

"They want to put senators on the spot. Ads will be running. Trust me," said Durbin, who added that the Republicans were trying to "change the subject" of the election away from the war in Iraq and the economy.

One commercial already was running on radio in South Dakota, where former Rep. John Thune, who supports the amendment, is challenging Senate Democratic Leader Tom Daschle.

"The institution of marriage is under fire from extremist groups in Washington, politicians, even judges who have made it clear that they are willing to run over any state law defining marriage. They have done it in Massachusetts and they can do it here," Thune says in the commercial. Daschle has said he will oppose the amendment.

In a string of speeches during the day, Republicans said their motivation was the defense of marriage, the well-being of children and a desire to prevent unelected judges from amending the constitution from the bench.

"There is a master plan out there from those who want to destroy the institution of marriage to, first of all, begin to take this issue in a few select courts throughout this country at the state level," said Sen. Wayne Allard, R-Colo. Pointing to rulings in Vermont and Massachusetts, he said that "once they get their favorable rulings from activist judges ... they want to take it to the federal courts and they'll eventually move it to the Supreme Court."

In a strongly worded speech, Sen. Rick Santorum, R-Pa., said some criticism runs along these lines: "Marriage is hate. Marriage is a stain. Marriage is an evil thing. That's what we hear. People who stand for traditional marriage are haters, they're bashers, they're mean-spirited, they're intolerant. ... Well, we're not," he added.

Several Republican senators have argued in private meetings in recent days that their leaders are making a political mistake by trying to force the amendment to a vote. One lawmaker said there were fresh expressions of concern at a weekly closed-door meeting during the day.

At the same time, several aides said Santorum and Sen. Gordon Smith of Oregon both urged fellow Republicans to support the measure on the test vote, depicting it as an issue of loyalty to the GOP leaders.

Smith has been among Republicans expressing concern about the amendment as drafted, saying he prefers a simpler one-sentence version. The officials spoke on condition of anonymity, citing the confidentiality of the discussions.

Under the Constitution, it takes a two-thirds vote by both houses of Congress to submit an amendment to the states. Approval by three-fourths of the state legislatures is required to complete ratification.