Last year, gay-rights advocates nationwide celebrated when New York became the sixth and by far the largest state to legalize same-sex marriage. This year, they may have four times as many reasons to celebrate.

Currently, the only places in the United States where same-sex couples can get marriage licenses are Connecticut, Iowa, Massachusetts, New Hampshire, New York, Vermont and the District of Columbia. Same-sex marriage is constitutionally banned in 28 states, and most others ban it by statute.

But polls show public opinion shifting toward greater acceptance of gay rights, and four states -- Maine, Maryland, New Jersey and Washington -- are actively pursuing legislation or ballot measures that would legalize same-sex marriage. Previous efforts have failed in Maine, Maryland and New Jersey, but the climate has changed, and it is very possible that by the end of 2012, there will be 10 states that allow same-sex marriage.

Maine

The fight to legalize same-sex marriage in Maine has had some interesting twists and turns. The state legislature voted to legalize it in the spring of 2009, and then-Gov. John Baldacci signed the bill, but opponents put a referendum on the ballot that November, and voters rejected same-sex marriage by a margin of 53 percent to 47 percent. The new law never went into effect, and the issue was put on hold for more than two years.

Now it's back, but supporters of same-sex marriage are approaching it from the opposite angle this time. The state legislature has moved toward the Republicans recently, and it would be unlikely to pass the sort of bill it did in 2009. But public opinion has shifted in the opposite direction, so now it is same-sex marriage supporters, and not opponents, who are relying on the ballot box. An LGBT advocacy group, Equality Maine, gathered enough signatures to put a referendum on the ballot this November, and supporters are optimistic that it will pass, based on the results of an October 2011 Public Policy Polling survey. According to that poll, 51 percent of Maine voters believe same-sex marriage should be legal, and only 42 percent disagree.

Maryland

The Maryland Senate approved a bill to legalize same-sex marriage in 2011, but the measure died in the House, largely out of concern that if it passed, voters would overturn it by referendum. Now legislators are trying again. A new bill is waiting for a Senate vote, which might not happen for several weeks. If it passes the Senate and the House -- which is likely, as both chambers are strongly Democratic -- it will go to Gov. Martin O'Malley, a Democrat who supports same-sex marriage, for his signature.

If the bill passes, it probably will lead to a referendum, but supporters of same-sex marriage have more reason to be confident this time around: a Washington Post poll conducted in January showed that 50 percent of Maryland voters support same-sex marriage and only 44 percent oppose it.

New Jersey

New Jersey has allowed civil unions, which provide same-sex couples with many of the same rights as marriage, since 2007, but an effort to legalize marriage failed in 2010. Now, the state legislature is again considering a same-sex marriage bill. Supporters have more than enough votes to pass the bill in both the Senate and the Assembly. The question is whether they can secure enough votes to override a veto, because Gov. Chris Christie, a Republican, is a vocal opponent of same-sex marriage.

In theory, if the legislative effort failed and a referendum were placed on the November ballot, as Christie advocates, same-sex marriage should still prevail: according to a Quinnipiac poll conducted in January, New Jersey voters support same-sex marriage by a margin of 52 percent to 42 percent. If the veto override is successful, or if the voters pass a referendum, New Jersey will become the seventh state to legalize same-sex marriage -- or the eighth, if Washington gets there first.

Washington

Of the four states considering legalizing same-sex marriage, Washington is the closest to actually doing so. The state Senate passed a bill on Wednesday by a vote of 28-21, the state House is expected to do the same, and by the end of February, it should be on the desk of Gov. Christine Gregoire, a Democrat, who has promised to sign it.

Opponents of the Senate bill tried unsuccessfully to attach an amendment that would have put the issue of same-sex marriage up to a public referendum in November, but Washington residents who oppose same-sex marriage are now trying to gather enough signatures to get the referendum on the ballot anyway. If they collect enough signatures and voters reject same-sex marriage, that would override the legislature's efforts. But if voters back same-sex marriage, or if opponents fail to get enough signatures to hold the referendum, Washington will become the seventh state in the country to allow same-sex couples to marry.

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