As oil continued to pour into the Gulf of Mexico on a recent Saturday, Jennifer Wilkerson spent three hours on the phone talking about life after petroleum.

For Mrs. Wilkerson, 33, a moderate Democrat from Oakton, Va., who designs computer interfaces, the spill reinforced what she had been obsessing over for more than a year  that oil use was outstripping the world’s supply. She worried about what would come after: maybe food shortages, a collapse of the economy, a breakdown of civil order. Her call was part of a telephone course about how to live through it all.

In bleak times, there is a boom in doom.

Americans have long been fascinated by disaster scenarios, from the population explosion to the cold war to global warming. These days the doomers, as Mrs. Wilkerson jokingly calls herself and likeminded others, have a new focus: peak oil. They argue that oil supplies peaked as early as 2008 and will decline rapidly, taking the economy with them.

Located somewhere between the environmental movement and the bunkered survivalists, the peak oil crowd is small but growing, reaching from health food stores to Congress, where a Democrat and a Republican formed a Congressional Peak Oil Caucus.