In a dramatic turn of events, the chair of a committee in the Maryland House of Delegates cast the deciding committee vote on Friday for a same-sex marriage bill, keeping the bill alive and allowing it to go the floor of the House for a final vote next week.

Del. Joseph Vallario (D-Prince George’s County), chair of the House Judiciary Committee, indicated earlier that he would likely not vote for the bill. But he cast a “yes” vote on Friday when it became known that another committee member and co-sponsor of the bill, whose support faltered earlier in the week, would vote against it.

The committee voted 12 to 10 to approve the bill and send it to the floor of the House of Delegates.

The vote to approve the bill came after the committee defeated several proposed amendments introduced by opponents aimed at weakening or gutting the bill, including a proposal for civil unions.

“Securing a favorable committee vote was an enormous obstacle – one that we were able to overcome together as thousands of marriage supporters called, emailed, and met with their delegates,” said Morgan Meneses-Sheets, executive director of the statewide LGBT group Equality Maryland.

“But I’m hearing from our elected officials that out-of-state opposition is flooding  their offices with slanderous lies about gay and lesbian couples and their families like never before,” Meneses-Sheets said.

She called on LGBT Marylanders and their friends and supporters to redouble their efforts to contact their delegates to ask for their support in the final vote expected next week on the floor of the full House of Delegates.

Vallario’s vote in favor of the Civil Marriage Protection Act in committee on Friday became the deciding vote allowing the measure to pass after Del. Tiffany Alston (D-Prince George’s County), a co-sponsor of the bill, voted against it.

Alston was one of three Democratic co-sponsors of the bill whose support wavered earlier this week.

Alston and Del. Jill Carter (D-Baltimore City) forced Vallario to cancel a scheduled vote on the bill on Tuesday when they failed to show up for the voting session. Both said their initial intent was to pressure the committee and Democratic leaders in the House of Delegates to devote more attention to other bills they believe were equally as important as same-sex marriage.

Following meetings and phone calls with colleagues and constituents, the two agreed to show up for a committee voting session on Friday. Carter said she expected to vote for the bill. Alston, however, told the Baltimore Sun she was praying over how to vote, saying her religious beliefs made her uncomfortable despite her decision earlier in the year to become a co-sponsor of the bill.

Meanwhile, Del. Sam Arora (D-Montgomery County), another co-sponsor of the bill who pledged support for same-sex marriage in his election campaign last fall, stunned LGBT activists earlier in the week when he said he, too, was having strong reservations over the bill based on personal religious beliefs.

Political observers say support for same-sex marriage is strong in his solidly Democratic and liberal-leaning district in Montgomery County.

Arora released a statement Friday morning, shortly before the committee session, saying he had decided to vote for the bill in committee and on the House floor, with the expectation that voters would ultimately decide the issue in an expected referendum next year.

“I have heard from constituents, friends, and advocates from across the spectrum of views and have thought about the issue of same-sex marriage extensively,” he said in his statement.

“While I personally believe that Maryland should extend civil rights to same-sex couples through civil unions, I have come to the conclusion that this issue has such impact on the people of Maryland that they should have a direct say.”

Carter voted for the bill in committee. She has not said how she will vote when the measure reaches the full House next week.

Sources familiar with the committee said one of the proposed amendments called for dropping the same-sex marriage language and converting the legislation into a civil unions bill.

The marriage bill won approval last week in the Maryland Senate.

Supporters were cautiously optimistic that the razor-thin majority of delegates in the House of Delegates who committed to back the bill just a few weeks ago would hold firm and not buckle under a furious campaign to kill the bill by a coalition of conservative religious groups, including the Catholic Archdiocese of Maryland.

Arora’s initial statements that he might not vote for the bill drew a firestorm of protest from LGBT activists and others in Montgomery County, who noted that his pledge of support for the marriage bill played a role in their decision to support him and contribute money to his campaign for his House seat in last November’s election.

“We applaud the Maryland House of Delegates Judiciary Committee for ending attempts to hold our families hostage to political maneuvering,” said Joe Solmonese, president of the Human Rights Campaign, an LGBT advocacy group that’s lobbying for the Maryland marriage bill.

“Maryland is at the forefront in the fight for equality and will go down on the right side of history,” he said. “We ask the full House to swiftly move forward to bring full equality to Maryland families.”

Marc Solomon, national campaign director for the LGBT advocacy group Freedom to Marry, also praised the action of the committee but cautioned supporters to continue to push hard with lawmakers in the days before the final vote.

The National Organization for Marriage, which is leading efforts to defeat the bill, has said it would take immediate steps to place the same-sex marriage law before the voters in a referendum if it passes in the legislature and Gov. Martin O’Malley signs it, as he has said he would.

If opponents succeed in obtaining the required number of petition signatures, such a referendum would appear on the ballot in November 2012 in the midst of the U.S. presidential election campaign.