Washington - (RNS) Unless mainline Protestant churches can refocus their energies and trim their public agenda, they risk losing their historic and important voice on social issues, scholars said at a conference here on Friday (March 16).

For decades, the mainline churches -- Methodists, Lutherans, Presbyterians and others -- have quietly fed the homeless, nursed the sick and pushed a progressive social agenda in Washington. They rarely sought publicity for their work, and largely agreed to work with anyone who shared their mission.

But there is a growing sense that perhaps the quiet voice of the mainline churches is not loud enough in the public sphere, and that maybe the churches have taken on so many projects that their influence has become diluted.

"We have to ask whether by taking on everything ... the mainline has spread itself too thin and therefore has fewer success stories to share," said James Wind, president of the Alban Institute, an organization which studies congregational life.

The two-day conference on Capitol Hill was sponsored by the Aspen Institute, a Washington think tank.

In an age when denominational labels matter less and less, Wind said the mainline churches must link with Roman Catholics and evangelicals on projects where they can be truly effective.

That's the same strategy being discussed by the venerable National Council of Churches -- a group of 36 mainline, Orthodox and historically black churches -- as it recovers from financial chaos and searches for a new mission in the 21st century.

Together, the mainline churches represent a potentially powerful army of 22 million members in 75,000 congregations. They take in $11 billion in collections annually, and mainline Protestants are more likely than evangelical Protestants to be involved in civic affairs, volunteer programs and community organizations.

Robert Wuthnow, a Princeton University scholar and leading mainline researcher, said the churches must learn to work with, and not simply on behalf of, groups they are trying to support. In particular, Wuthnow said, mainline churches have long been committed to racial justice but have been unable to craft an alliance with predominantly black church groups.

"Of all the issues we studied, this was the one in which mainline efforts had the least success," Wuthnow said. Sometimes the churches suffer from a bad case of "moral laryngitis," he said.

There is evidence that decades of membership decline in the mainline churches has leveled off, and that attendance on Sunday mornings actually may be on the rise.

In the past 20 years, the mainline churches have been eclipsed by the larger-than-life personalities of the religious right. But Wuthnow said most mainline Christians are more comfortable with working behind the scenes than the more public ventures of Pat Robertson and Jerry Falwell.

"There is reason to be happy with what the mainline churches have been doing; there is reason, too, to get busy and think harder about what the churches should be doing in the future," Wuthnow said.

"There is still reason to believe that God is with the church, guiding it and sustaining it in these challenging times."