Although proponents of same-sex marriage legislation thought they only had one more vote in the Senate after the bill passed the state’s House of Delegates on Friday, Sen. Ed Reilly (R-Anne Arundel) has proposed amending the bill, making its passage all the more uncertain.

The House vote was thought to be the biggest obstacle in getting the bill to Gov. Martin O’Malley, who has pledged his support for the legislation, since the chamber killed the bill last legislative session. But if Reilly’s amendment to the legislation — which would put the measure in place Oct. 1, 2012, rather than Jan. 1, 2013— is accepted in a Senate hearing tomorrow, the House would have to vote once again — and many supporters said they are concerned the body will oppose the measure in a second vote.

“It would require the bill to get cleared again by the House,” Sen. Brian Frosh (D-Montgomery) said. “The reason for the amendment was to kill the bill.”

While the Senate was supposed to vote on the amendment yesterday, Reilly requested to delay the hearing by one day.

“This is an important issue for all of us,” he said during yesterday’s hearing. “I don’t have a sense that we need to rush through this.”

The same-sex marriage bill that passed the House has its enactment date set for Jan. 2013 to provide sufficient time for a referendum, since many opponents have pledged to launch a petition effort to put the measure on the November ballot if passed.

Sen. Jamie Raskin (D-Montgomery) said Reilly’s amendment is simply a way to stall the bill’s passage and to try to kill it before it reaches O’Malley’s desk.

“I don’t see the logic of it, and I think that we all know that any effort to amend the bill at this point is essentially to kill the bill,” he said before the Senate yesterday. “It may look like a placebo, but it is a poison pill and I would urge the supporters of this legislation to resist it.”

But many lawmakers said they still expect the bill to pass and do not believe an amendment would change any legislative votes. Senate President Mike Miller (D-Calvert and Prince George’s) said he doesn’t “anticipate a single vote has changed” since last legislative session’s 25-21 Senate vote.

Frosh, however, said amendments would threaten the bill’s future by making it go through a House vote a second time; he said he expects favorable results in the Senate.

“I’m certainly hoping that we’re not going to adopt any amendments,” he said. “I think we have the votes as long as nobody gets sick.”

Frosh added he believes passage of the bill is an important measure for equality.

“In a couple of years it will be very clear that it’s very mainstream,” he said. “I think people will look back on the debate today in 10 years, maybe five years, and ask, ‘what were they thinking?'”

Raskin said because the bill has been amended to address religious concerns of many lawmakers who feared such legislation would force churches to recognize same-sex unions, it warrants passage.

“It provides that no church and no church-operated institution will ever be required to solemnize, celebrate or promote any marriage that it chooses not to for religious reasons,” he said.

He added he believes it is a right that should be afforded to thousands of residents who are currently ineligible for more than 400 benefits and more than 1,000 federal benefits.

“The Supreme Court has said that deadbeat fathers have a right to marry, mass murderers on death row have a right to marry, people who just met on Who Wants to Marry a Millionaire have the right to marry,” he said. “Yet there are tens of thousands of our constituents who still cannot marry.”

bach@umdbk.com