The hearing is expected to be one of the largest — and longest — of the 2012 legislative session. With supporters about six votes shy of the 71 they need for passage in the chamber, the small collection of undecided members will determine the bill's fate.
Two panels, the House Judiciary Committee and the Health Government and Operations Committee, will take testimony jointly, meaning 45 delegates will have the chance to grill witnesses.
Adding to the drama, a second controversial measure will be before them. Besides O'Malley's Civil Marriage Protection Act, which would legalize same-sex marriages, the delegates will also examine the Maryland Marriage Protection Act, a bill with a similar name that would have the opposite effect.
The House is of particular focus this year because it's so evenly split. The Senate passed a same-sex marriage bill last year, and both sides acknowledge that the votes are there again. Supporters did not have enough votes in the House last session, so both sides have used the past year to shore up support.
The bill to ban same-sex marriage is given no chance of passage, but the list of its sponsors makes clear who is against O'Malley's legislation. Fifty-six of the 141 House lawmakers put their names on O'Malley's bill. Forty-six signed on to the other one, a constitutional amendment perennially introduced by Del. Don Dwyer to define marriage as between a man and a woman.
That leaves 39 who aren't on either bill, but many of them have either publicly or privately committed to support one side or the other in the same-sex-marriage debate.
"Many times legislation does come down to four or five individuals who haven't made up their minds," Busch said.
One of those is Del. Pam Beidle, an Anne Arundel County Democrat who plans to attend Friday'shearing even though she's not a member of either committee. "It is difficult when half of my district supports it and half doesn't," Beidle said. "I haven't made a decision."
She says she's "personally torn."
Beidle finds that her meetings with the parents of same-sex couples are persuasive. "If I had a child who was gay, who had a lifelong partner, I'd want them to be happy," she said. "It is not my job to judge someone else's moral decision."
At the same time, Beidle, a practicing Roman Catholic, says she hears from Cardinal-elect Edwin F. O'Brien, who opposes the bill. He stresses to Beidle the significance of marriage to their shared religious community and the extent to which he believes O'Malley's bill would undermine that institution.
"This is a difficult issue," Beidle said. "It is truly fifty-fifty."
Like several other lawmakers interviewed, she said that she'd prefer to merely throw the question to the voters by passing a measure that would put it before them as constitutional amendment, similar to how the General Assembly handled slot machine gambling. But doing so would require 85 votes, more than simple passage of a bill.
Though support for O'Malley's bill in the House Judiciary Committee is considered shaky, activists on both sides say that between the two committees there are enough votes to move it to the floor. Several options could be used: One committee could approve it and the other not vote. Or the 45 members of the two committees could vote collectively, with a simple majority bringing the bill to the floor.
One of the few members of the Health Government and Operations Committee members who haven't publicly said how he'll vote is Del. Robert Costa, an Anne Arundel County Republican and self-described "recovering" Catholic. An occasional maverick who has supported other gay-rights bills, he says that he has wrestled with the issue.
"Republicans typically believe in lesser government," Costa said. "So how do you explain this position to the public? Government saying who can and cannot be married?"
On the other hand, he's struggling with whether the institution of marriage is accurately viewed as a government function. "Is it an arrangement between individuals and the government?" he asked. "Or between the individuals and God?"
"I want to hear from both sides," said Costa.
Costa listened closely last year to how his constituents came down on the issue, keeping staff working nights to carefully unclog a voice-mail system not designed to handle the thousands of calls he received. To him, every message mattered.
Yet, he's apt at rebuffing sophisticated lobbying efforts from activists. He declined to see the parent of a gay lawmaker, saying he did not believe the meeting would be helpful.
When he suspected that a visit from a GOP colleague would turn into a pitch against same-sex marriage, he began filibustering, talking to the lawmaker at length about an unrelated health issue.
Other members simply do not want to talk about same-sex marriage publicly.
"Why don't you ask me about the fiscal issues that I'm involved with?" asked Del. Mary Dulaney James, a Democrat who represents Harford and Cecil counties. James, who is on the Appropriations Committee, declined to say how she would vote or discuss how she would make up her mind.
A new factor this year is O'Malley's involvement. He included the bill in his legislative package, hosted a breakfast for supporters at Government House and then held a news conference on the front steps. He testified briefly at the Senate hearing, and is expected to be at the witness table during Friday'shearing.
He's also working behind the scenes. Last week he made a rare trip to the House Judiciary Committee to pull aside Del. Jill Carter, a Baltimore Democrat. Last year she sponsored the House bill, but confounded advocates when she, along with another co-sponsor, walked out of a committee voting session on the bill.
The move slowed the bill's momentum and is widely seen as having given opponents more time to organize.
Carter ultimately voted for the bill in committee, but this year decided not to put her name on the legislation.
She characterized her recent talk with O'Malley as a "nice conversation" that covered his same-sex-marriage bill in addition other parts of what she described as his "very challenging" legislative agenda. She declined to say how she will vote.
Del. Michael Smigiel, a Republican, inadvertently interrupted the meeting last week and joked that the governor was putting pressure on the delegate. "As I walked away, I could hear the breaking of bones," he quipped.