This presidential transition will be the most difficult since Abraham Lincoln entered office. Although President-elect Barack Obama is not facing a civil war, he will inherit an agenda of staggering uncertainty as the nation teeters on the edge of economic collapse.

The next six weeks will make Franklin Delano Roosevelt's transition seem less daunting by comparison. Roosevelt faced a great economic calamity, too, but the nation was not at war, the federal government was tiny and the transition was six weeks longer. Also, Herbert Hoover had done so little to address the economic crisis during his last year in office that Roosevelt had a clean slate on which to write the New Deal.

Obama's success depends in large measure on the transition infrastructure designed eight years ago by former White House chief of staff and current transition director John Podesta. He could not have known that Obama would be the first president-elect to use the tools he championed, but designed them so that even a former Illinois state senator with four years in national office would benefit.

Obama must use that infrastructure to pass three tests.

First, Obama must start pushing about 3,000 political appointees through a notoriously sluggish vetting process. Designed during the McCarthy era, when everyone in government was suspected of being a communist, the process is best viewed as a concrete pipe that can handle a only small number of names at a time, usually on a first-come, first-served basis. Congress gave the FBI authority to begin vetting transition aides from both campaigns months before Election Day. Because many of these aides will end up in line for positions, the Obama administration will almost certainly set a record in the number of early nominations.

Nothing guarantees quick Senate approval, however. The big problem in the Senate is not the filibuster, which is rarely used against nominees, but personal holds designed to extract executive concessions.

Even the most principled senator has been known to use the tactic. Angered by the Senate's opposition to his $1.8 billion railroad rescue bill, Sen. Joseph R. Biden Jr., D-Del., informed his colleagues in March 2002 that he had just placed the first two holds of his distinguished career. "I do not know what else to do," he told his colleagues, "stand on my head in the middle of the well to get the attention of people around here?" Obama's trusted adviser former Senate Majority Leader Thomas A. Daschle is no doubt already at work brokering deadlines to force faster confirmations, but old habits are hard to break.

Second, the next president must decide how to decide. If the campaign is prologue, Obama is likely to use John F. Kennedy's collegial approach, which emphasizes open, sometimes interminable discussion among senior advisers en route to consensus. However, he will soon discover that he needs a more disciplined process built around a strong chief of staff. Democratic presidents are particularly vulnerable to this awakening. They often enter office promising maximum access only to find they are soon drowning in advice. Absent some formalization, they drift through the transitions squandering resources as they ponder possibilities, not realities.

Third, Obama must narrow his priorities to a precious few. There will be no New Deal or Great Society next year. By intent or accident, the Bush administration has done a masterful job constraining the next president's agenda through his tax cuts and mistakes. Obama can use some of these calamities to create a sense of urgency for tax cuts, economic stimulus and a deadline for troop withdrawal from Iraq.

But he must also recognize the brevity of his influence. Even with a landslide victory in 1964 behind Lyndon B. Johnson and a massive Senate and House majority on his side, he worried about the erosion of support. "You've got to give it all you can that first year," he later said. "Doesn't matter what kind of majority you come in with. You've got just one year when they treat you right and before they start worrying about themselves."

No matter how well he does on these first three tests, Obama's greatest challenge will be deciding when to say no. Potential appointees are already lined up like airplanes over Chicago's O'Hare International Airport, while urgent appeals for action are flowing into the transition team from every conceivable approach.

Obama would do well to install a wall of industrial-strength paper shredders as a first line of defense against the onslaught. Forced to defend many of Johnson's now-rusting Great Society programs against a cacophony of claims, Obama may soon find that he will be doing more talking about grand ideas than signing laws.

Paul C. Light is the author of "A Government Ill Executed: The Decline of the Federal Service and How to Reverse It" and a professor at New York University's Robert F. Wagner Graduate School of Public Service.

(Nov. 5, 2008)