Still, experts on religion and politics agree that the religious left has a way to go to catch up to the religious right in organizational strength and that there are structural barriers that could prevent it from happening.
"When you look at religious progressives, generally, they come in many different varieties," says John Green, a senior fellow at the Pew Forum on Religion and Public Life.
Some are theological liberals who happen to be politically liberal, some are theological conservatives who happen to be politically liberal, and some are a bit of both, Mr. Green says. And they come from different backgrounds – evangelical, Catholic, mainline Protestant. So while religious conservatives can easily organize within their congregations, for the religious left it is more complicated. Also, adds Green, "people on the liberal side of these debates tend toward ecumenism and interfaith. A lot of Reform Jews might be considered part of this. Certainly, black Protestants would be part of this."
A look at the numbers also shows a religious left that is still on the beginning end of a trajectory movement leaders hope will make it a major force in shaping political and policy debate. At this week's four-day Pentecost conference sponsored by Sojourners, there are 600 people in its attendance. At its height in the mid-1990s, the Christian Coalition could summon 4,000 people to Washington for its annual convention. And while that organization has faded, the religious right's top mass gathering – now sponsored by the Family Research Council and allied groups – was able to draw 1,700 attendees to a Values Voter Summit in 2006, with another scheduled for this fall, according to Joe Conn of Americans United for Separation of Church and State.