A constitutional amendment to define marriage as a union between one man and one woman stalled Wednesday in a 49-48 vote, but conservative backers say they are pleased to have had the vote nonetheless.

“For thousands of years, marriage — the union between a man and a woman — has been recognized as an essential cornerstone of society. ... We must continue fighting to ensure the Constitution is amended by the will of the people rather than by judicial activism,” said Senate Majority leader Bill Frist, R-Tenn., after the vote.

A constitutional amendment needs two-thirds votes to pass, but first had to get through the procedural cloture vote, which requires 60 senators to agree to end the debate and move toward final passage.

Shy 11 votes to go to a final debate, few crossed the political aisle to vote against their party's majority position. Republican Sens. John McCain, Susan Collins, Olympia Snowe, Judd Gregg, Arlen Specter, Lincoln Chafee and John Sununu voted against the cloture vote. Democratic Sens. Ben Nelson and Robert Byrd voted for it, as they did in 2004.

Republican Sen. Chuck Hagel and Democratic Sens. Chris Dodd and Jay Rockefeller were absent.

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A two-thirds majority would have been required to send an amendment to the states for ratification by three-quarters of the union. But since constitutional amendments originate in the Senate, failure to get it through that body means any vote in the House is purely for ceremony.

Trying to put the best spin on it, Senate supporters said they were pleased with Wednesday's outcome.

"There's many of us who have not had an opportunity to debate and discuss this," said Sen. Mel Martinez, R-Fla., a freshman who gave his support to what has become a near-perennial vote.

"We're building votes," said Sen. David Vitter, R-La., another supporter who cast his first vote on the issue on Wednesday. "That's often what's required over several years to get there, particularly to a two-thirds vote."

President Bush, who several times in the last week called for passage of the amendment, also expressed his satisfaction with the outcome.

"Today’s Senate vote on the Marriage Protection Amendment marks the start of a new chapter in this important national debate. ... Our nation’s founders set a high bar for amending our Constitution -- and history has shown us that it can take several tries before an Amendment builds the two-thirds support it needs in both houses of Congress. My position on this issue is clear: marriage is the most fundamental institution of our society, and it should not be redefined by activist judges. The people must be heard on this issue," he said in a statement.

A majority of Americans define marriage as a union of a man and a woman, as does the amendment, according to a new ABC News poll. But just as many oppose amending the Constitution, the poll found.

Forty-five of the 50 states have acted to define traditional marriage in ways that would ban same-sex marriage — 19 with their own state constitutional amendments and 26 with statutes.

"Most Americans are not yet convinced that their elected representatives or the judiciary are likely to expand decisively the definition of marriage to include same-sex couples," said McCain, R-Ariz., a possible presidential candidate in 2008. He voted against the procedural maneuver to end debate.

Jody M. Huckaby, executive director of Parents, Families and Friends of Lesbians and Gays (PFLAG), said the vote was one of discrimination versus fairness.

"Forty-nine of our elected leaders voted to support legislation that would write discrimination against our loved ones into the Constitution. ... Without a shred of credible evidence, they shamefully concluded that ‘traditional’ marriages would be torn apart if we were to grant all Americans equal rights, and used this as their justification for their extreme position," Huckaby said in a statement.

"On the other hand, 48 of our legislators displayed great courage and wisdom in opposing the Federal Marriage Amendment. Whether they voted no because they believe that this bill is discriminatory, or because they believe that this should be left to the states and not a federal mandate, or because they believe this to be a deeply misplaced priority, they have made a tremendous statement. Their votes prove that this political pandering will not be tolerated," the statement continued.

The House plans a vote on the amendment next month, said Majority Leader John Boehner, R-Ohio.

"This is an issue that is of significant importance to many Americans," Boehner told reporters. "We have significant numbers of our members who want a vote on this, so we are going to have a vote."

Like the Senate, the House in 2004 fell short of the two-thirds vote needed.

The Associated Press contributed to this report.