I don’t know about the track record of Christopher Ketcham, the author of this Radar piece explaining the "big thing" that that made Jim Comey object to the warrantless wiretapping program so aggressively in March 2004. But it sounds like a plausible explanation.
Ketcham describes a database of Americans who, in case the government ever implements its Continuity of Government program in a time of national emergency, can be rounded up and jailed.
… a number of former government employees and intelligence sources with independent knowledge of domestic surveillance operations claim the program that caused the flap between Comey and the White House was related to a database of Americans who might be considered potential threats in the event of a national emergency. Sources familiar with the program say that the government’s data gathering has been overzealous and probably conducted in violation of federal law and the protection from unreasonable search and seizure guaranteed by the Fourth Amendment.
According to a senior government official who served with high-level security clearances in five administrations, "There exists a database of Americans, who, often for the slightest and most trivial reason, are considered unfriendly, and who, in a time of panic, might be incarcerated. The database can identify and locate perceived ‘enemies of the state’ almost instantaneously." He and other sources tell Radar that the database is sometimes referred to by the code name Main Core. One knowledgeable source claims that 8 million Americans are now listed in Main Core as potentially suspect. In the event of a national emergency, these people could be subject to everything from heightened surveillance and tracking to direct questioning and possibly even detention.
Another well-informed source—a former military operative regularly briefed by members of the intelligence community—says this particular program has roots going back at least to the 1980s and was set up with help from the Defense Intelligence Agency. He has been told that the program utilizes software that makes predictive judgments of targets’ behavior and tracks their circle of associations with "social network analysis" and artificial intelligence modeling tools. [my emphasis]
Ketcham goes on to explain that the Bush Administration was cross-referencing Main Core with its warrantless wiretap program. Read more