Some opponents have threatened a filibuster, but Senate leaders say they are confident they have the votes to end debate.

If the bill passes the Senate, it moves to the House, traditionally the more liberal chamber on social policy. Gov. Martin O'Malley (D) has said he will sign the bill.

The Maryland vote comes the same day that the Obama administration announced it will no longer defend the constitutionality of the Defense of Marriage Act, the federal law prohibiting recognition of same-sex marriage.

Maryland Senate Minority Leader Nancy Jacobs (R-Harford) acknowledged that a same-sex marriage bill is all but certain to pass in her chamber Thursday and said there are no plans for a filibuster.

"It definitely will pass," Jacobs said. "I don't think it's going to be extremely long. We all know the outcome of this."

She said she expects several senators to speak on the bill on Thursday but does not anticipate the need for a motion to cut off debate.

"I don't think that's going to happen," Jacobs said.

She said Republicans had deliberately tried to keep the tone of Wednesday's debate civil. "It was nobody's desire to become rancorous or over-emotional," she said. "We wanted to stick to the facts."

The so-called "2nd reader" vote advancing the bill in Maryland came after the Senate rejected several other amendments.

The Senate voted 31 to 16 to reject an amendment that would have prohibited the "promotion" of same-sex marriage in public elementary schools.

The chamber also voted 26 to 21 to strike part of the title of the same-sex marriage bill, which had been known as the "Religious Freedom and Civil Marriage Protection Act." The title is now the "Civil Marriage Protection Act."

Sen. C. Anthony Muse (D-Prince George's) argued that the bill had nothing to do with religious freedom as it is historically understood. A separate amendment to change the bill title to "Same-Sex Marriage" failed on a 28 to 19 vote.

Update, 11:50 a.m.:
The Senate has defeated two more amendments. One amendment that was soundly rejected on a voice vote would have exempted clerks of court from performing same-sex marriages based on religious objections. Opponents said public officials take an oath to do their jobs. Another failed amendment would have exempted public school teachers who do not want to teach materials that "promote" same-sex marriage. That amendment was defeated 30 to 15.

Update, 11:15 a.m.:
The Senate rejected 30 to 17 an amendment that would have allowed religious-affiliated adoption agencies, such as Catholic Charities, to refuse services to same-sex couples. Opponents argued that it was discriminatory and conflicted with current adoption regulations, which do not allow organizations to discriminate based on sexual orientation or other factors.

Update, 10:43 a.m.:
The Senate has adopted by voice vote an amendment that says a "fraternal benefit society" controlled by a religious organization, such as the Knights of Columbus, is not required to provide insurance benefits to an individual if it violates the group's religious beliefs. The provision is modeled after one in Vermont's law.

Update, 10:32 a.m.:
Floor debate is under way. The Senate has adopted by voice vote an amendment that makes clear religious organizations do not have to promote same-sex marriages through educational programs, counseling, retreats or summer camps. A similar provision is the District's law allowing gay unions.

Original post:
Debate is scheduled to begin on the Maryland Senate floor shortly after 10 a.m. Wednesday on the highest-profile social issue of the legislative session: legalizing same-sex marriages.

Senators are expecting a lengthy and emotional discussion over a bill that would remove a provision in Maryland law limiting marriages to a man and a woman. The legislation also states that religious organizations and affiliated groups are not required to participate in weddings or celebrations that conflict with their beliefs.

Prospects for passage are considered good, because a majority of senators in the 47-member chamber have pledged support for the bill. The Judicial Proceedings Committee gave the bill a 7-to-4 favorable vote last week.

Early debate Wednesday is expected to focus on a number of amendments, including some that would alter the "conscience clause" affecting religious organizations. Senators are expected to break early in the afternoon and return that night to consider more amendments.

A final Senate vote on the bill, which could face a filibuster attempt, is not expected for a couple of days.

If the bill passes the Senate, it moves to the House, traditionally the more liberal chamber on social policy. Gov. Martin O'Malley (D) has said he will sign the bill.

You can listen to the debate here, and we will post updates as votes are taken on amendments and other motions.