Four separate and competing national organizations representing various streams of atheists, humanists and freethinkers will soon be spreading their gospel through advertisements on billboards, buses and trains, and in newspapers and magazines.
The latest, announced on Tuesday in Washington, is the first to include spots on television and cable. This campaign juxtaposes particularly primitive — even barbaric — passages from the Bible and the Koran with quotations from nonbelievers and humanists like Albert Einstein and Katharine Hepburn.
The godless groups say they are mounting this surge because they are aware that they have a large, untapped army of potential troops. The percentage of American adults who say they have no religion has doubled in the last two decades, to 15 percent, according to the American Religious Identification Survey, conducted by researchers at Trinity College in Hartford and released in 2008. But the ranks of the various atheist organizations number only in the tens of thousands.
That is one reason for the multiple campaigns: the groups are competing with one another to gain market share, said Mark Silk, founding director of the Greenberg Center for the Study of Religion in Public Life, which is also at Trinity College.
“There’s a competitive environment for ‘no religion,’ and they’re grabbing for all the constituents they can get,” Mr. Silk said.