Some in Washington have called for a congressional probe, others for an independent "blue-ribbon" commission.
All but lost amid the flying rhetoric about presidential "missed warnings" and congressional "second-guessing," a panel of lawmakers has already begun sifting through documents in a post-9/11 quest to find and plug gaps in America's intelligence networks.
The question before Congress is whether this existing panel, or some new body, will press forward in a review of security matters tied to the terrorist threat.
More broadly, lawmakers must wrestle with whether airing past mistakes would help build crucial momentum for reform or devolve into a blame game.
"The issue shouldn't be gotcha politics about the president, because the president didn't know a lot. The focus should be why didn't our intelligence community have the information," says Rep. Porter Goss (R) of Florida, chairman of the House Permanent Select Committee on Intelligence, who is cochairing the House/Senate panel with Sen. Bob Graham (D) of Florida. In Mr. Goss's view, the panel can do the job. "We are well down the road on a diagnosis of what is wrong, and there is still more to come."
Members of the intelligence committees in both houses of Congress who make up this panel and some two dozen staff have been perusing "a smothering amount of information" for more than three months, including documents from Afghanistan and information from detainees. A major concern is that disclosure not "contaminate evidence" needed in court cases, says Goss.
Other lawmakers are calling for a more independent investigation. In the Senate, a bipartisan group including Sens. Joseph Lieberman (D) of Connecticut, John McCain (R) of Arizona, Robert Torricelli (D) of New Jersey and Charles Grassley (R) of Iowa are calling for a 14-member blue-ribbon panel of private citizens to bring a "fresh, open-minded" approach to the inquiry.
"The obvious advantage of a Congressional investigation, as opposed to a blue-ribbon panel, is that Congress has the authority to act, and that can be very important. The disadvantage is that it would tend to be partisan, because of the high degree of partisanship in the Congress today," says former Rep. Lee Hamilton, director of the Woodrow Wilson Center.
One of the items at the heart of the fingerpointing last week was a 1999 report prepared for the CIA that suggested that terrorists might use planes to fly into buildings, such as the Pentagon. Critics say the report failed to raise the alerts in intelligence circles that it should have.
But intelligence experts say there was nothing new in that suggestion. In 1995, an arrest in the Philippines produced evidence that Ramzi Yousef, who had planned the 1993 World Trade Center bombing, had plans to hijack 11 airliners and fly them into the White House and CIA.
"That operational aspect was known. Anybody could have had it. There's a lot more being read into the significance of this report against the background of what was known at the time than the report merits," says John Gannon, former CIA deputy director for intelligence, who chaired the panel that reviewed this report.
"To some degree, you'll find Congress was part of the problem here. Congress was informed by its intelligence committee of these concerns, and couldn't do any better job of prioritizing to solve the problem," he adds.
Dianne Feinstein (D) of California is introducing legislation this week calling for an independent head of the intelligence community, separate from the Director of the CIA.
She has also asked the FBI to explain why a July 2001 memo from the its Phoenix office warning that several Arabs were suspiciously training at US aviation schools did not set off alarms in Washington.
A similar issue came up when the nation tried to investigate the attack on Pearl Harbor in 1941. At issue in a series of investigations was whether or not to reveal to the public (or investigators) that the US had broken the Japanese war codes. Just before the 1944 election, Republican candidate Thomas Dewey learned that the US had broken the Japanese codes, but administration officials persuaded him to not raise the issue in his presidential campaign, lest the nation lose its edge in the Pacific war. Dewey agreed, but later wrote said it cost him the race.
Congress launched its own investigation in September 1945. "The crisis of the war kept Congress quiet" until then, says Senate Historian Richard Baker.
It's unclear whether lawmakers will be as forgiving in today's climate. But over the weekend, some of the president's harshest critics toned down their remarks. "Democrats seemed just a little too eager to get into this, and people picked up on that," says Larry Sabato, a political scientist at the University of Virginia.