The two men “planned to drive their vehicle as fast as they could toward Obama shooting at him from the windows,” according to an affidavit filed in federal court in Jackson, Tenn., by an agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives. Mr. Obama has no plans to be in Tennessee, and the affidavit does not make clear whether the men had picked a place for an attack.

Image Daniel Cowart of Bells, Tenn., was one of two men charged in what officials called a white supremacist assassination plot. Credit... Associated Press

The assassination was to be the culmination of a “killing spree” that would also single out children at an unnamed, predominately black school, federal officials said. The men talked of “killing 88 people and beheading 14 African-Americans,” according to the affidavit.

The two men each had “very strong views” about Aryan white power and “skinhead” ideology, the federal officials said, and the numbers 88 and 14 have special significance in the white power movement. The number 88 is shorthand for “Heil, Hitler”  H is the eighth letter in the alphabet and 14 signifies a 14-word mantra among white supremacists: “We must secure the existence of our people and a future for white children.”

Officials said the two men met via the Internet through a mutual friend.

Concerns about possible plots against Mr. Obama have been acute because of his status as the first black presidential nominee from a major party. He has had Secret Service protection since May 2007, the earliest a candidate was ever assigned protection.

Mr. Cowart and Mr. Schlesselman were each charged with illegal possession of a sawed-off shotgun, conspiracy to rob a firearms dealer and making threats against a presidential candidate. A detention hearing is scheduled for Thursday in Memphis.