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.
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.