ONE OF the big political stories of 2009 has been the surge in American public approval for gay marriage and the growing number of states - including the heartland bastion of Iowa - that have legalized the practice, but here in Pennsylvania the pages of this political thriller are still blank.

Even as the neighboring states of New York and New Jersey seem to be racing to legalize gay marriage, perhaps as early as this year, advocates for gay rights in Pennsylvania find themselves still locked in a defensive posture. Indeed, Republican state Sen. John Eichelberger, of Blair County, intends today to introduce an amendment to the state constitution aimed at blocking any courts from approving same-sex marriage in the Keystone State.

"Clearly, Pennsylvania is among Alabama and Mississippi in terms of gay rights," said Malcolm Lazin, the executive director of the Equality Forum, the gay-rights-advocacy group based in Philadelphia.

Lazin and other activists say that same-sex marriage will need to wait until the issue garners more local support and that their main priority is to promote legislation that will add Pennsylvania to the ranks of a majority of other states in offering full workplace protection to gays and lesbians.

Some experts believe that Pennsylvania will eventually join the list of states - which now includes Massachusetts, New Hampshire, Vermont, Iowa, Connecticut and Maine, as well as the District of Columbia - that have legalized gay marriage or are about to and, in fact, that the day of reckoning might come sooner than people expect.

Nate Silver, the former baseball-stats guru who's now among the nation's top analysts of political data, recently created a map predicting when all 50 states would legalize same-sex marriage, and - based on factors such as the power of a state's evangelical religious movement - listed Pennsylvania as a state that would recognize gay marriages in 2012.

But though pundits based here expect a day when gay marriage will gain approval in Pennsylvania - thanks to the overwhelming support for the practice among voters younger than 40 - they say that any real movement could be closer to a decade away because of the state's unique demographic factors.

These experts note that Pennsylvania is still one of the three oldest states in the country, with disapproval of gay marriage still running high among seniors. The state is also heavily Catholic, they note, and home to other populations, including conservative religious sects in central Pennsylvania, as well as African-Americans here in Philadelphia, who trend toward higher gay-marriage-disapproval ratings.

"We have population loss, less mobility, less education, and a brain drain so that the people we have that are educated are leaving the state," added G. Terry Madonna, the political scientist and pollster from Franklin & Marshall College, recalling the blue-collar, socially conservative "Rea-gan Democrats" who dominated politics in western Pennsylvania in the 1980s and '90s. Polling has shown that support for gay marriage rises with education levels.

"All of that makes for a serious problem for gay-rights activists," he said.

The most recent polling data shows that Pennsylvania continues to trail the rest of the United States, especially some of its neighbors along the Eastern Seaboard, when it comes to voicing support for same-sex marriage.

Indeed, the national numbers from an ABC News/Washington Post poll released late last month were stunning: The survey showed that a plurality of Americans for the first time backed same-sex marriage, with support skyrocketing from just 36 percent three years ago to 49 percent today, while opposition had crumbled from 58 percent down to 46 percent.

The numbers are similar in New Jersey, which socially is quite liberal, has a high number of independent voters and already allows civil unions. (Washington, Oregon, Maryland and Hawaii offer certain partnership rights to gay couples, short of marriage.)

The April poll from Quinnipiac University showed that the Garden State had tipped in favor of supporting same-sex marriage, with 49 percent in favor and 43 percent opposed.

It's not surprising, then, that New Jersey Gov. Jon Corzine along with the state's top two lawmakers, all Democrats, have said that they'll support a measure to legalize gay marriages, although state pundits say that passage isn't likely until 2010, because some legislators facing re-election this year will want to hold off on what they still perceive as a politically divisive issue.

It's different here in Pennsylvania. The most recent public-opinion survey, from Muhlenberg College and the Allentown Morning Call, published earlier this month, showed that backing for gay marriage in the Keystone State increased from a paltry 35 percent in 2004 to 42 percent. The public is now split down the middle on a statewide constitutional amendment to ban gay marriage, which remains a leading agenda item for conservative lawmakers.

This changing climate no doubt encouraged Gov. Rendell to recently sign off on benefits for the domestic partners of state employees, similar to a measure enacted when he was mayor of Philadelphia in the 1990s.

Yet lobbyists say that they expect as soon as this week a renewed push in Harrisburg for a constitutional amendment to ban gay marriage - modeled after measures enacted in some 30 states, many just in the last couple of years after a state court ruling legalized same-sex marriages in Massachusetts.

The amendment, which requires approval from lawmakers, then a statewide ballot, has fallen short in the Legislature the last two sessions. Pennsylvania did enact a law in 2006 that defines marriage as between a man and a woman, but advocates want an amendment that would prevent a future judicial ruling to overturn that law and allow gay marriages.

"The only way that we can get the people to decide this issue is through the ballot box," said Michael Geer, president of the Pennsylvania Family Institute, which strongly supports a statewide ban on gay marriages similar to one enacted in the neighboring states of Ohio and West Virginia.

He said that the measure is critical for defending and strengthening families in Pennsylvania.

"Marriage as defined as between a man and a woman has proven to be the best for the health, education and welfare of children," he said.

Not only do advocates for same-sex marriage disagree with that, but they argue that anything short of full marriage for homosexuals - including civil unions recognized by state and local governments - simply doesn't go far enough to offer full protection on issues such as family-leave time, medical-visitation rights or eviction rights.

Andy Hoover, legislative director for the American Civil Liberties Union, said that although a serious push in Pennsylvania for same-sex marriage will need to wait behind legislation aimed at protecting the rights of gays in the workplace, he believes that the state's politicians will catch up to rising public support, eventually.

"The political community tends to be behind the general public," said Hoover, who noted that Pennsylvania's system of electing judges may also make quick, dramatic action on the marriage issue unlikely.

Jeremy Mayer, director of the master's program in public-policy at George Mason University, in Virginia, said that political momentum doesn't always go one way, noting that the Equal Rights Amendment for women seemed unstoppable in the 1970s until the measure faltered in conservative Southern and Midwestern states.

In this case, however, he predicted that there may be federal action on gay marriage when opposition dwindles to a handful of states over the next 10 to 15 years.

However, one hurdle to federal action remains: President Obama, despite overwhelming support from gay voters, has said that he supports civil unions but not gay marriage. *