Temple Oheb Shalom and Har Sinai Congregation, stalwart synagogues in the history of Reform Judaism in Baltimore, are considering a merger after decades of declining membership.

Officials at each synagogue have notified congregants of the possibility. Steering committees have been meeting to weigh the logistical and cultural implications.

And an official with Union for Reform Judaism, the umbrella organization for the Jewish denomination in North America, is helping each synagogue’s leadership sort through the potential challenges and benefits of a permanent union.

Mina Wender, the president of Temple Oheb Shalom, and Anne L. Berman, the president of Har Sinai, say the two sides haven’t come to a final decision, but they’ve been engaged in serious talks for more than three months, and thus far the signs have been so positive that they’d be surprised if the merger didn’t happen.

“In the best of all possible worlds, two years from now we’ll be celebrating the High Holidays in one house,” Berman said.

A merger would mean a coming together of two synagogues that have played key roles in the history of Jewish Baltimore.

Har Sinai, Baltimore’s first Reform congregation, was founded in 1842 as an alternative to Baltimore Hebrew Congregation, then an Orthodox synagogue and the largest Jewish congregation in the city.

Eleven years later, according to a Jewish Museum of Maryland historical account, a group of “up-and-coming” German immigrants founded Oheb Shalom in Baltimore “as amidway alternative to Har Sinai’s radical Reform and Baltimore Hebrew Congregation’s continued (yet increasingly fractious) Orthodoxy.”

Each has a history of involvement in social justice advocacy, from the days when the firebrand Reform Rabbi David Einhorn, long the leader of Har Sinai, advocated abolition of slavery before and during the Civil War — an unpopular stance in conservative Jewish Baltimore — through the 1960s, when rabbis from both synagogues took part in civil rights marches alongside the Rev. Martin Luther King Jr.

The current talks come against a backdrop of declining membership at many non-Orthodox synagogues — and a drop in commitment to formal faith practices in the United States in general.

A widely publicized 2015 study by the Pew Research Center, for example, showed that the number of American adults who describe themselves as Christian dropped by about 8 percentage points between 2007 and 2014, and the number of those who describe themselves as religiously unaffiliated — as atheists, agnostics or “nothing in particular” — jumped by more than 6 percentage points during the same span.

Among American Jews, only the Orthodox have showed robust demographic gains over the past decade and a half, while the less strictly observant branches, including Reform and Conservative, have seen sharp declines by many measures, including the number who attend services regularly, belong to synagogues and donate to Jewish foundations.

Pew also found in a 2013 survey of Jewish Americans that more Jews in their 20s describe themselves as nondenominational than any other segment, followed closely by those in their 30s.

“In 40 years, far fewer Jews will identify as Conservative and Reform, and far more will identify as Orthodox,” Steven M. Cohen, a professor of Jewish social policy at the Hebrew Union College-Jewish Institute of Religion in New York, wrote in Forward magazine last month.

The trend has shown itself clearly at places such as Har Sinai and Oheb Shalom, where the presidents say membership has been declining steadily over the past half-century or so, to the point where, Wender said, “it’s time to take action.”

When Berman joined Har Sinai in the late 1970s, she said, membership was about 800 families, and when Wender became a member at Oheb Shalom in 1982, nearly 1,000 families belonged.

Membership at Har Sinai, now located in Owings Mills, is down to about 325 families. At Oheb Shalom, in Park Heights, it’s about 625.

The change represents a nearly 50 percent collective drop-off — enough that Wender said Oheb Shalom “has been operating on a bare-bones budget” for some time.

At Har Sinai, Berman said, the feel of the worship experience has changed dramatically.

When Berman first joined, she said, “we had to open up the sanctuary and line up chairs all the way back into the social hall” for every service.

“We don’t fill it up anymore,” she said.

The two — who have been friends for decades — met one afternoon this week at McDonogh School in Owings Mills, where Wender has taught math for more than 40 years. The conversation was cheerful and upbeat, even as the presidents listed reasons for declining membership locally: increased mobility, greater competition for members’ time and resources, a growing secularization of the culture.

Both say the declines have constrained their capacities to provide the kinds of programs that would foster growth — including worship services aimed at divergent demographics.

A blended synagogue could offer a youth-friendly service as well as services targeting young adults and baby boomers, for example, and high school and adult programs now operating independently could be combined. It also would create one of Baltimore’s larger Reform congregations.

Rabbi David Fine of the Union for Reform Judaism has presided over “easily 40 or 50” such mergers across the country over the past two decades, including many that never got past the discussion stage, helping to produce successful partnerships in about half a dozen. “Such unions have become increasingly common” in Reform Judaism, said Fine, a director of consulting and transition management for the organization.

Fine’s view is that the demographics aren’t all bad. The Reform movement has added a net 12 synagogues in the United States over the past year, for example, even if the internal congregation numbers present a more complicated picture.

In any case, Fine — who has been consulting with Har Sinai and Oheb Shalom officials for weeks — said the need for partnerships has helped Reform communities focus their missions, compelling them to choose what matters most. “I think that we’re becoming less silo-ized; we’re asking how we can we move from independence to interdependence, toward cooperation,” he said. “I think we’re seeing that in the religious world, we don’t lose our identity by partnering. We get back to who we are and why we exist. It allows us to think about big questions. The congregations that are most successful think about these big questions.”

A five-person steering committee at each synagogue has been at work since the summer, talking through such questions as how to unify governing philosophies, merge financial plans and blend liturgical approaches. The next step: appointing subcommittees chosen from within the congregations to focus on each such issue.

At Har Sinai and Oheb Shalom, the presidents said, feedback from congregants has been almost uniformly positive, in large part, they believe, because members of the congregations — which stand less than five miles apart, each armed with a similar vision — already know each other from years of social interaction and common work on philanthropic projects.

The presidents compared the ongoing process to a courtship — “we like each other; we’re getting to know each other; we might go steady, but we haven’t set a date yet,” Wender said — and Berman believes that if and when a marriage takes place, it will be a healthy one.

“Along the way, we’ll work out our preferences together,” she said, “and that’s what a congregation is really about.”

jonpitts@baltsun.com