The spree, which initially targeted an unidentified predominantly African-American school, was to end with the two men driving toward Obama, "shooting at him from the windows," the documents show.
"Both individuals stated they would dress in all-white tuxedos and wear top hats during the assassination attempt," the court complaint states. "Both individuals further stated they knew they would and were willing to die during this attempt."
An Obama spokeswoman traveling with the senator in Pennsylvania had no immediate comment.
Sheriffs' deputies in Crockett County, Tenn., arrested the two suspects - Daniel Cowart, 20, of Bells, Tenn., and Paul Schlesselman 18, of Helena-West Helena, Ark. - Oct. 22 on unspecified charges. "Once we arrested the defendants and suspected they had violated federal law, we immediately contacted federal authorities," said Crockett County Sheriff Troy Klyce.
The two were charged by federal authorities Monday with possessing an unregistered firearm, conspiring to steal firearms from a federally licensed gun dealer, and threatening a candidate for president.
Cowart and Schlesselman were being held without bond. Agents seized a rifle, a sawed-off shotgun and three pistols from the men when they were arrested. Authorities alleged the two men were preparing to break into a gun shop to steal more.
Jasper Taylor, city attorney in Bells, said Cowart was arrested Wednesday. He was held for a few days in Bells, then moved over the weekend to another facility.
Until his arrest, Cowart lived with his grandparents in a southern, rural part of the county, Taylor said, adding that Cowart apparently never graduated from high school. He moved away, possibly to Arkansas or Texas, then returned over the summer, Taylor said.
Attorney Joe Byrd, who has been hired to represent Cowart, said in a written statement that he was was investigating the charges against his client and would have no further comment. Messages left on two telephone numbers listed under Cowart's name were not immediately returned.
No telephone number for Schlesselman in Helena-West Helena could be found immediately.
The court documents say the two men met about a month ago on the Internet and found common ground in their shared "white power" and "skinhead" philosophy.
The numbers 14 and 88 are symbols in skinhead culture, referring to a 14-word phrase attributed to an imprisoned white supremacist: "We must secure the existence of our people and a future for white children" and to the eighth letter of the alphabet, H. Two "8"s or "H"s stand for "Heil Hitler."
Court records say Cowart and Schlesselman also bought nylon rope and ski masks to use in a robbery or home invasion to fund their spree, during which they allegedly planned to go from state to state and kill people. Agents said the skinheads did not name the African-American school they were targeting.
Jim Cavanaugh, special agent in charge of the Nashville, Tenn., field office for the Bureau of Alcohol, Tobacco Firearms and Explosives, said authorities took the threats very seriously.
"They said that would be their last, final act - that they would attempt to kill Sen. Obama," Cavanaugh said. "They didn't believe they would be able to do it, but that they would get killed trying."
He added: "They seemed determined to do it. Even if they were just to try it, it would be a trail of tears around the South."
An ATF affidavit filed in the case says Cowart and Schlesselman told investigators the day they were arrested they had shot at a glass window at Beech Grove Church of Christ, a congregation of about 60 black members in Brownsville, Tenn.
Nelson Bond, the church secretary and treasurer, said no one was at the church when the shot was fired. Members found the bullet had shattered the glass in the church's front door when they arrived for evening Bible study.
"We have been on this site for about 120 years, and we have never had a problem like this before," said Bond, 53 and a church member for 45 years.
The investigation is continuing, and more charges are possible, Cavanaugh said. He said there's no evidence - so far - that others were willing to assist Cowart and Schlesselman with the plot.
At this point, there does not appear to be any formal assassination plan, Secret Service spokesman Eric Zahren said.
"Whether or not they had the capability or the wherewithal to carry out an attack remains to be seen," he said.
Zahren said the statements about the assassination came out in interviews after the men were arrested last week.
The Secret Service became involved in the investigation once it was clear that an Obama assassination attempt was part of the plot. Obama received a Secret Service detail in May 2007, the earliest a candidate has ever been assigned protection, in part because of his status as a prominent black candidate.
"We don't discount anything," Zahren said, adding that it's one thing for the defendants to make statements, but it's not the same as having an organized assassination plan.
Helena-West Helena, on the Mississippi River in east Arkansas' Delta, is in one of the nation's poorest regions, trailing even parts of Appalachia in its standard of living. Police Chief Fred Fielder said he had never heard of Schlesselman.
However, the reported threat of attacking a school filled with black students worried Fielder. Helena-West Helena, with a population of 12,200, is 66 percent black. "Predominantly black school, take your pick," he said.
Associated Press writers Erik Schelzig in Nashville, Tenn., Jon Gambrell in Little Rock, Ark., and Eileen Sullivan in Washington contributed to this report.