The arrests Monday in an alleged neo-Nazi assassination plot against Sen. Barack Obama involve one of a handful of serious threats against the Democratic presidential candidate, federal law enforcement sources tell ABC News.
The officials say Obama has been the target of well over 500 threats, most of which are not taken seriously.
But in an estimated dozen or so cases, the threat was considered serious enough that law enforcement agents were assigned to track down suspects.
Threats of violence, harsh invective, language such as "get rid of" or "kill" or "eliminate" are all considered triggers for possible investigation, officials say.
But in only a handful of cases, did the threat, after being run down by United States Secret Service, have the elements that warranted it to be taken extremely seriously.
The methamphetamine-fueled plot against Obama that surfaced during the Democratic convention in Denver is considered by law enforcement officials to be a good example of the kind of ill-conceived, unlikely-to-succeed threat that nevertheless involved high-powered rifles and disguises.
It was only because of a traffic stop arrest that the plot was discovered, authorities say.
In the case of today's arrests in Crockett County, Tennessee, it was a burglary in progress run that led law enforcement to uncover the twisted plan to assassinate Obama.
Officials said the two Tennessee men arrested, Daniel Cowart and Paul Schlesselman, told the Secret Service they first planned to kill 102 African Americans and then "dress in all white tuxedos and wear top hats during the assassination attempt" of Obama.
Authorities say both men have strong racist views and met on the internet through the website of a white supremacist neo-Nazi group called the Supreme White Alliance (SWA).
Morris Dees, the founder of the Southern Poverty Law Center (SPLC) in Alabama, says that the "extremely violent skin head" group has chapters now in six states and a couple of foreign countries.
"They believe there is going to be an uprising of white people in American," said Dees, "and if they can kill Obama, it will bring on the white revolution."
In response to SPLC claims that Cowart and Schlesslman are tied to the SWA, SWA issued a statement saying, "The Southern Poverty Law Center has lied again. Stating on their website that the two young men arrested yesterday on charges accusing them of plotting to assassinate the presidential candidate Barak Oboma (sic) and go on some sort of killing spree are tied to the SWA. One of the young men was in fact a probate earlier this year but was ousted by the SWA before the SWA had a president. Since this time none of the SWA members have had any contact with the accused. So before you get your story wrong, (SPLC) get the facts."
In a few cases that the Secret Service has investigated, one individual has written hundreds of threat letters in an effort to capture the candidate's attention, officials say.
In another case dismissed as not serious, the individual making the threat tried to repeatedly call the director of the Secret Service to register the threat.
Officials say there have been far fewer threats against Republican presidential candidate Sen. John McCain.
Each candidate has a security detail of equal size, considered a "vice-presidential level" size, according to law enforcement officials. Secret Service agents are augmented by a heavy presence of state and local police, but in uniform and undercover.