About 60 investigators from 20 local agencies in the region were assigned to gather intelligence about threats, including any directed against Obama, Denver FBI chief Jim Davis says. Teams of federal agents and local police rousted confidential sources in search of information.
"We weren't picking anything up," he says. "It was very quiet."
That changed at 2:24 a.m. Aug. 24 — the day before the convention started — when a suburban Denver police officer stopped a blue 2008 Dodge pickup.
A search of the truck, court documents show, turned up bullet-resistant body armor, wigs, two rifles with mounted scopes, walkie-talkies and a device that braces firearms for more accurate firing.
Police relayed their findings to a federal intelligence center in Denver, which sent 100 investigators to the streets.
The truck driver led agents to four other associates. One of them, according to court documents, told investigators that two of his colleagues had discussed a plan to "kill" Obama by setting up a high-powered rifle on a vantage point overlooking Invesco Field at Mile High, where Obama was to deliver his acceptance speech.
"Assuming that this was a credible plot, we had to ask ourselves: 'Do we have everybody involved?' " Davis says. "At that point, there was no degree of certainty that we had."
Investigators pursued leads as far away as Kansas. Analysts used satellite technology to try to pinpoint possible locations from which a high-powered rifle could reach the speaker's podium.
Yet, almost as quickly as the threat appeared, it began to "melt down," Davis says.
Within 18 hours, interviews with the suspects and other investigative efforts revealed that none had ties to white supremacist groups. The alleged plot against Obama, agents concluded, was a product of apparent drug-induced bluster. The weapons and other suspicious equipment were related to the suspects' involvement in the methamphetamine trade.
Eight days before the election, the Bureau of Alcohol, Tobacco, Firearms and Explosives said it had foiled a bizarre assassination plot against Obama by two men whom prosecutors said could have links to the white supremacist movement.
The men, who were charged with weapons violations and making threats, allegedly planned a killing rampage that would have begun at a predominantly African-American school and ended with an attack on Obama.
ATF spokesman Robert Browning immediately noted that the loosely organized plot raised questions about whether the suspects could have carried it out.
Even so, former FBI agent Mey says Obama's election has the potential to reinvigorate the radical right, a mix of militia and patriot groups that thrived during the Clinton administration.
In the wake of Obama's election, white supremacist leaders are claiming a surge in membership, according to the Southern Poverty Law Center, which monitors the groups' activities.
While Obama was giving his stirring acceptance speech in Chicago on Nov. 4, former Ku Klux Klan leader David Duke was rallying the white supremacist movement in a provocative call to action, saying Obama's election represented a "night of tragedy and sadness."
"Barack Obama has long history of antagonizing white people," Duke said in an audio message broadcast on the radical website Stormfront.org. "We as European Americans have to rally for our survival."