On one level, the debate is about logistics: Where and how would lawmakers assemble if the Capitol were destroyed, heavily damaged or targeted in a bioterror attack?
The House, in particular, also must resolve sticky constitutional questions. Not the least of them is whether a devastated legislative body could choose a speaker, who would be behind only the vice president in the line of succession to the presidency.
Many lawmakers believe that on Sept. 11, United Airlines Flight 93 was headed for the Capitol, the symbol of American democracy, before an apparent passenger uprising led to its crash in a Pennsylvania field. Just minutes earlier, the biggest symbols of U.S. economic and military might had been attacked in New York City and suburban Virginia.
Both the House and Senate were disrupted a few weeks later when an anthrax-laced letter was opened in the office of Senate Majority Leader Tom Daschle of South Dakota.
Combined with the continuing threat from the al Qaeda network and other terrorists, the events have led to a wholesale re-examination of how Congress would continue if many of the 435 House members and 100 senators were killed or seriously injured.
"Those who believe there will always be time to address this, and we can postpone a solution indefinitely, are engaging in wishful thinking," said Rep. Brian Baird, a Washington Democrat pressing for changes.
House and Senate leaders have discussed a number of sites, such as Fort McNair in the District of Columbia, as temporary emergency meeting places. Other sites up to 1,000 miles away are being considered. House Speaker Dennis Hastert, R-Ill., got $100 million included in a supplemental spending bill last week to build and outfit what would be a de facto capitol with necessary communications and computer technology.
Rep. Jim Langevin, D-R.I., is advocating greater use of the Internet or video conferencing technology as an alternative, especially if lawmakers were stranded in home districts because airlines were grounded and other modes of transportation shut down.
His idea might get a tryout in the months ahead. Each House member already has a new handheld communications device for maintaining contact.
Beyond such post-emergency planning is the more fundamental question of how Congress, and especially the House, would reconstitute itself if many lawmakers were killed or incapacitated.
New senators could be chosen quickly because governors can appoint successors. House members, however, must be chosen by direct elections that can require up to six months.
Lest anyone think the matter trivial, consider the legislation Congress passed quickly after Sept. 11: authorization of military force, emergency rescue aid, airline aid, money for the war on terrorism, assistance to victims and a law enforcement anti-terrorism bill.
Under the Constitution, none of that could have been be done by the Senate or a president alone.
"It is hard to argue that at a time of maximum national peril, it would be desirable either to have laws made by an unrepresentative handful of lawmakers or via a benign form of martial law," said Norman Ornstein of the American Enterprise Institute.
Baird and 86 others have proposed a constitutional amendment to allow governors to appoint House members for a 90-day term if 25 percent of the House has been killed, disabled or is missing and presumed dead.
Replacements would not have to be of the same political parties as their predecessors. That is an important difference between Baird's proposal and a plan by Sen. Arlen Specter, R-Pa., and that could ensnare the idea in partisan politics.
Passing a constitutional amendment also could take years. An amendment would have to pass both houses of Congress by two-thirds vote and be ratified by three-fourths of the states.
Many lawmakers say Congress should focus instead on changing its rules or passing laws to address the most pressing problems.
For instance, a law could call for expedited election of replacements and address the presidential succession question by preventing a small number of House members from picking a speaker. A rules change could redefine a voting quorum needed to pass emergency legislation.
A bipartisan group of lawmakers plans meetings this summer intended to recommend a course of action. The co-chairman, Rep. Christopher Cox, R-Calif., wants Congress to act this year.
By CURT ANDERSON