Editor's note: Paul Moses, professor of journalism at Brooklyn College of the City University of New York, is the author of "The Saint and the Sultan: The Crusades, Islam and Francis of Assisi's Mission of Peace."
(CNN) -- For about a week, the nation's Catholic bishops enjoyed some measure of their bygone political clout.
The bishops launched a vigorous grassroots campaign to protest a rule from the Obama administration's health care mandate that would force many Catholic institutions to cover birth control through their employee health plans.
Catholic churchgoers have seen such campaigns attempted before, with bishops issuing stinging denunciations that are repeated in church publications and in letters read to parishioners at every Mass.
But this time, to the surprise of many, the bishops' effort seemed to work. President Barack Obama quickly modified the rule. He didn't satisfy the bishops -- but still, the clergymen had upset the political calculus that they no longer affect Catholic voters.
The bishops were able to wield influence because their message against the contraception mandate was framed in a way that appealed to a broad spectrum of Catholics. For moderates and liberals, there were calls to freedom and conscience, rather than blunt declarations to heed ecclesial authority. For conservatives, there was the opportunity to circle the wagons against secularism.
But if the bishops insist on coming across as shrill and partisan, as some are wont to do, they'll wind up once again preaching to half the choir.
Moderate and liberal Catholics won't stand behind the bishops if they perceive a partisan position. And it won't take much to trigger that reaction because certain bishops were transparently opposed to Obama during the 2008 election campaign, and many more of them later maligned the University of Notre Dame for granting the president an honorary degree.
I noticed a letter to the editor in the diocesan newspaper in Brooklyn, where I live, that captures the unease I believe a good number of Catholics feel. The writer said she understood the church's position on the birth-control mandate, but she practically pleaded with the editor, who had accused the Obama administration of pushing socialism, to take a less polarizing tone.
If the bishops really want to gain back some of the clout they used to hold, they would do well to consider the community organizing tactics that their own parishes have adopted in many poor urban neighborhoods. It is an approach that relies heavily on building consensus.
Guided by the writings of Saul Alinsky, coalitions of houses of worship have organized around specific issues, such as a plan to build low-cost housing. The community organizers' first step was to secure the enthusiastic support of parishioners, demonstrated through massive rallies. Once pastors really do speak for their people, they are then in a position to demand that elected officials of whatever party support their agenda.
Obama once was a community organizer for just such a church-funded coalition, working from a Catholic rectory on Chicago's South Side. Like the Chicago politicians he encountered as a young man, Obama knows that a church's grassroots campaign is only as effective as it is unified.
I'm not sure how many bishops know that.
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The opinions expressed in this commentary are solely those of Paul Moses.