Sen. Edward M. Kennedy, D-Mass., voiced "strong opposition" to the amendment, which says marriage should be defined as a "union of a man and a woman."
"A vote for this amendment is a vote for bigotry pure and simple," Kennedy said in a statement released later. "It makes no sense, for the first time in our history, to amend the Constitution by writing discrimination back into it."
The Judiciary Committee passed the amendment, 10 to 8, along party lines.
Democrats opposed the measure, which they say is being pushed by the Republican majority to rally conservative voters in a crucial midterm election year.
In an emotional clash before the vote, the panel's chairman yelled "good riddance" at Sen. Russell Feingold, a Wisconsin Democrat, who strode out of the ornate Capitol room in protest of the "terrible" amendment.
Feingold claimed that the meeting's rapid change of venue from its usual site in a Senate office building stymied public attendance.
"I don't need to be lectured by you," Chairman Arlen Specter, R-Penn., angrily told Feingold.
"If you want to leave, good riddance!"
Feingold responded: "I enjoyed your lecture, too. See ya, Mr. Chairman."
The full Senate is expected to vote on the constitutional amendment the week of June 5. Support of two-thirds of Congress and three-fourths of state legislatures are required to change the U.S. Constitution, which has been amended 27 times.
Sen. Sam Brownback, the conservative Kansas Republican who's leading the amendment effort, said after the vote that his motives are not election related.
"Mine is not a political viewpoint," he said. "Mine, I believe, is for the future of this country."
The move comes amid plummeting popularity of President Bush and the Republican Party, which positioned itself against gay marriage during the 2004 elections. Several states during that election placed measures on their ballots defining marriage as between a man and woman.
Vermont Sen. Patrick Leahy, the senior Democrat on the Judiciary Committee, derided the amendment at the meeting as a political strategy aimed at encouraging a conservative turnout at the polls in November.
Turning to Sen. Orrin Hatch, a Utah Republican of Mormon faith, Leahy mocked that Congress could ratify a constitutional amendment against polygamy the practice by some outlaw Mormons of marrying multiple wives.
Polygamy is a felony. And Leahy insinuated that Hatch, who admitted to knowing of certain polygamists, is complicit in its existence.
"I've met some who are very sincere, but I don't justify it," Hatch said of polygamists.
Leahy countered: "Well if you know they're out there committing a felony and you haven't reported it then you..."
Hatch interjected: "Don't accuse me of wanting polygamy."
The meeting's unusual location the small but ornate President's Room, adjacent to the Senate chamber spurred criticism by Democrats who said few members of the press and public could attend.
Several senators were standing during the meeting due to limited seating, and there was no television coverage. Specter said he'll oppose the amendment during the full Senate vote.
Other Republicans, though, have expressed concern that Massachusetts' gay marriage law and Vermont's civil union law will encourage widespread gay marriages.
Kennedy dismissed GOP concerns, noting that nearly 7,000 gay marriages in the Bay State have not diluted the age-old sacrament.
"I'm proud that Massachusetts continues to be a leader on marriage equality for our citizens," Kennedy said. "We recognize that being part of a family is a basic right, and I look forward to the day when every state accepts this basic principle of fairness."
Evan Lehmann can be reached at email@example.com.