Washington (CNN) -- Maryland is poised to become the sixth state to recognize same-sex marriage as proponents say they believe they have enough support to pass such a measure in the upcoming legislative session.

The expansion of gay rights appears to have gained significant traction as Maryland's General Assembly begins its 90-day session Wednesday. Not only are Democrats optimistic about their chances of approving same-sex marriage, but a leading Republican, sensing momentum on the issue, has instead countered with a proposal to grant civil unions to gay couples.

Democratic Gov. Martin O'Malley has publicly stated that he would sign a marriage bill into law. Maryland then would join Massachusetts, Connecticut, Iowa, New Hampshire, Vermont and Washington, D.C., in sanctioning same-sex marriages.

Maryland has been inching toward granting greater rights and protections for members of the lesbian, gay, bisexual and transgender community. Last year Democratic state Attorney General Doug Gansler offered a legal opinion recognizing same-sex marriages performed in other jurisdictions.

"We've been marching in this direction for a while now," said Democratic state Delegate Heather Mizeur.

Mizeur, one of the state's seven openly gay legislators, said marriage is simply the expansion of other rights afforded gay couples in recent years, such as granting protections for hospital visitations and extending health insurance benefits.

"It just took a little while to get us there, but we're seizing the moment. It's our time," Mizeur said.

Democrats in Maryland fared much differently in the November elections than they did in rest of the nation when nearly two dozen state legislative chambers switched from Democratic to Republican control. Despite losing six seats in the House of Delegates, Maryland Democrats picked up two seats in the Senate and have maintained their supermajority in each chamber. The two-seat pickup in the Senate is viewed as the final hurdle needed for passage of the marriage bill. Given those dynamics, the Republican leader of the Senate is offering an alternative.

Acting as an individual and not as head of his caucus, Sen. Allan Kittleman told CNN that he wants to grant gay couples all the rights afforded to straight married couples under Maryland law without the stigma of religion.

"Civil unions would grant the same rights as marriage, but just shift the role of something that is viewed as a religious institution to something more secular," Kittleman said. "I just really believe, it is more the libertarian in me, that government needs to be out of something that is religious. The disagreement we have in society on gay marriage is from the religious aspects of it."

Calling same-sex relationships anything other than marriage is a nonstarter for gay rights advocates.

"We've taken those small steps forward. It's time to live with the promise that is marriage equality. No other institution provides the legal protections," said Morgan Meneses-Sheets, executive director of Equality Maryland, the state's largest LGBT rights group.

Six states -- California, Illinois, Nevada, New Jersey, Oregon and Washington -- currently grant same-sex couples all the same rights as marriages, short of the designation. Four other states -- Colorado, Hawaii, Maine and Wisconsin -- offer lesser levels of protections for gay couples.

But many other privileges of marriage, especially those regarding federal tax and entitlement programs, cannot be granted to same-sex couples, regardless of their states' marriage laws, due to the federal Defense of Marriage Act. That law requires the federal government to define marriage as a relationship between one man and one woman.

Even if same-sex marriage eventually becomes law in Maryland, opponents could collect 55,000 signatures and force a referendum on the subject in 2012.

Equality Maryland and its allies are expecting such a referendum to be held and said they are hopeful that it will be the first time that a same-sex marriage law is approved in a statewide popular vote.

"We're going to keep moving this issue forward until we all have marriage equality," Meneses-Sheets said.