The 49 to 48 Senate vote fell short of the 60 votes needed to clear a procedural hurdle, thwarting President Bush and the mostly Republican lawmakers who said the Constitution must be amended to prevent judges from striking down existing state bans on gay marriage.
Democrats accused Republicans of exploiting a divisive issue they knew would fail in order to shore up conservative support before November congressional elections and divert attention from topics like the war in Iraq that reflect poorly on the party in control of the White House and Congress.
"It is a cynical attempt to score political points by overriding state courts and intruding into individuals’ private lives," Democratic Sen. Edward Kennedy of Massachusetts said in floor debate on Tuesday.
The U.S. House of Representatives is expected to take up the marriage amendment in July, though Republican leaders do not expect it to pass there either.
"This is a big issue for lots of our members and frankly for lots of Americans," House Republican Leader John Boehner of Ohio told reporters on Tuesday.
Constitutional amendments must win approval from two-thirds of each house of the U.S. Congress and three-quarters of state legislatures before taking effect.
Colorado Republican Sen. Wayne Allard, the bill’s sponsor, did not expect the gay-marriage ban to pass but hoped to demonstrate increased support since 2004, when 48 senators voted for a similar bill.
Allard and other backers said they were not disappointed that the measure only won 49 votes this time.
"Clearly as time goes on there will be more votes in favor of this," said South Dakota Republican Sen. John Thune. "We make a little headway each time this is debated."
Seven Republicans voted against Allard’s bill on Wednesday, including two — Pennsylvania Sen. Arlen Specter and New Hampshire Sen. Judd Gregg — who supported it in 2004.
Specter said he opposes same-sex marriage but would vote against the measure because it tramples on states’ rights.
Two Democrats, Nebraska Sen. Ben Nelson and West Virginia Sen. Robert Byrd, voted for the gay-marriage ban.
According to a March 2006 poll by the Pew Research Center, 51 percent of Americans oppose same-sex marriage, down from 63 percent in February 2004.
Forty-five states have passed laws or amended their constitutions to prohibit same-sex marriage, and the 1996 Defense of Marriage Act allows states to refuse to recognize marriages performed elsewhere.
Allard said a constitutional ban is necessary to protect these laws, which in many cases were enacted with overwhelming public support.
State judges have struck down several state gay-marriage bans and court challenges are pending in nine states.
Since 2004, about 8,000 gay couples have married in Massachusetts, the only state to fully recognize same-sex marriages. Six other states and the District of Columbia offer same-sex couples some legal protections. (Additional reporting by Joanne Kenen)
© 2006 Reuters