After a nerve-rattling week in which the U.S. financial system was shaken to the core, here's a simple question: Why on Earth would anyone want to be president right now?

Even in the best of times, it's a grueling job. But the problems of 2008 seem unusually intractable, and despite the fine talk one sometimes hears about reconciliation, the electorate will be divided no matter who wins in November. Even Bush's snarkiest critics would have had trouble predicting all the rough weather of the second term, from Hurricane Katrina to the smoldering wars in Iraq and Afghanistan to the bursting of the housing bubble, the financial meltdown and the Recession That Dare Not Speak Its Name. Would any sane person want to inherit this?

Of course, even to pose that question assumes that candidates for the nation's highest office are normal reasoning creatures. Most of us would pause before spending millions of dollars to travel thousands of miles to eat hundreds of chicken dinners with people who snipe at our clothes, our hair cuts and our every public utterance. Losing is no fun, but is winning even worse? "Being president is like being a jackass in a hailstorm," Lyndon B. Johnson once said. "There's nothing to do but to stand there and take it."

So what does it mean to inherit the presidency in an hour of crisis? Historically, it has usually meant a push to reverse the last fellow's policies. That holds true even in relatively tranquil times. In 2001, for instance, the incoming Bush team, which scorned its predecessors as ineffectual, weak and morally compromised, made a mantra of the term "ABC" ("Anything But Clinton"). Their contempt was so thorough that a satirical headline in a story about the inauguration in the Onion read, "Bush: 'Our Long National Nightmare of Peace and Prosperity Is Finally Over.' "

Ironically, the outgoing Bush team may be in for similar treatment from the next crowd. With about 80 percent of the electorate saying that the country is on the wrong track, it doesn't take a brilliant tactician to suggest that a new direction would work well for either Barack Obama or John McCain. ("ABB" isn't terribly catchy; perhaps "ABBA," for "Anything But Bush Administration," might work better in the year of "Mamma Mia"?) As even McCain's campaign makes clear, anti-Bushism is likely to be the refrain of the early months of 2009, no matter who is elected.

But how well does rejecting the policies of one's predecessor work? Here's the historian's answer: pretty well. A glance at other difficult presidential transitions shows that in nearly every case -- though not quite all of them -- the presidency that came after a troubled one succeeded, in both senses of the word. And it usually did so by taking a brisk 180-degree turn.

The tradition of trampling on the last guy's policies is nearly as old as the presidency itself. It was hard for John Adams to improve upon George Washington, but it was easy for Thomas Jefferson's crowd to blast Adams. Abraham Lincoln started off under the worst conditions imaginable, but his majestic first inaugural address sent a clear message that James Buchanan's prevarications were a thing of the past. Grover Cleveland, the only president in history to succeed two different men, was able to declare a new beginning not once, but twice.

After Lincoln's, no presidency began under darker clouds than Franklin D. Roosevelt's. The U.S. financial system was in vastly worse shape than it is even today, totalitarianism was looming abroad, and the New York Stock Exchange had actually shut down. But Roosevelt knew that Herbert Hoover had given him, in FDR's own words, "an easy act to follow." On that dark inaugural day in 1933, the new president was only five sentences into his maiden speech when the sonorous attack on "fear itself" came; nothing was the same after that. Roosevelt launched a sustained attack on Hoover's laissez-faire policies; there's a reason he called the New Deal new.

Twenty years later, Dwight D. Eisenhower was able to inflict something of a GOP comeuppance on the Democrats at another anxious turning point in U.S. history. The beleaguered Truman administration was reeling from the Korean War, the Alger Hiss spy scandal, a housing crisis and the public's exhaustion with Democratic dominance. In 1952, Eisenhower became unbeatable simply by rising above these problems and promising to "go to Korea."

In office, Ike seemed to rescue the presidency. The moderate course he promised built confidence among Democrats as well as Republicans, and his personal probity let citizens hope for a new era free of influence-peddling and partisan attacks. Within two years of his inauguration, many of Harry S. Truman's worst problems had disappeared: The Korean situation stabilized, McCarthyism died an unmourned death, and Americans settled in for a long summer of prosperity in the middle of the 20th century.

In 1981, with the country in another deep funk after four years of stagflation, international setbacks and Jimmy Carter, Ronald Reagan borrowed from the example of his hero, FDR. Reagan was a natural anti-Carter -- a fact driven home on Inauguration Day, when Iran released the U.S. hostages it had been holding since Nov. 4, 1979.

Reagan did an about-face, and the public loved it. He could hardly take a false step during his early months, as seen in both his natural grace (most famously in his gallantry after surviving an assassination attempt) and his ability to bring some steel to the Oval Office (consider his confrontation with the air traffic controllers, a showdown that further bolstered his reputation as the anti-Carter). At the same time, he showed some willingness to reach across the aisle and made steady progress toward his ambitious goals of reducing the federal budget, lowering taxes and raising the defense budget. As the historian Sean Wilentz notes, "Not since President James K. Polk came to office in 1845 had any president succeeded in winning so much of his announced agenda so quickly."

But the formula of reversing a predecessor's policy doesn't always work so neatly. Consider Richard M. Nixon, who took over in 1969 from Lyndon Johnson, the miserable war president sunk by Vietnam. Nixon's presidency got off to a much better start than most of us remember. In his recent book, "Nixonland," historian Rick Perlstein reveals the surprisingly deferential treatment the new commander in chief received from the mainstream media (including The Washington Post and the New York Times), which persistently used such words as "cool," "confident" and "efficient" to describe him. To some extent, this was the natural result of national exhaustion with Johnson's bloated ego and bankrupt policies, which Nixon seemed to be reversing.

Vietnam was a harder problem to solve than Iraq, and in the early days, Nixon made real headway. Surprisingly, he showed a peacenik side, installing Woodrow Wilson's desk in his Oval Office, citing his mother's Quakerism in speech after speech and appearing to tamp down U.S. involvement in Southeast Asia -- a far cry from LBJ. His first budget proposed to reduce defense spending by $1.1 billion, and soon the New York Times could announce that "public pressure over the war has almost disappeared." When the first Americans landed on the moon in July 1969, Nixon was there to reap the credit. For a while, it seemed as if the sky was literally the limit to his political fortunes.

But of course, the story didn't end there. We now know that Nixon's reversal was incomplete and that he was giving in to his uglier instincts from the beginning. His apparent disengagement from Indochina was fatally undercut by his secret bombing of Cambodia: Starting in 1969, according to historian Larry Berman, more than 3,875 sorties were launched with no notification to Congress. From that evasion came a neverending stream of others, as well as a secret administration apparatus designed to conceal as many of them as possible. "We cannot escape history," Lincoln once said. Nixon proved the point by failing to separate himself from his predecessor as cleanly as he thought he had.

History cannot tell us who the 44th president will be. But history does suggest that a new commander in chief who charts a sharply different course from Bush will find an awfully receptive audience, at least in the early going. The next president will face daunting odds, trying to resolve two thorny conflicts, dismantle al-Qaeda, halt nuclear proliferation, contain a resurgent Russia, fight global warming and wring prosperity out of a battered economy.

But the best lesson history can teach is that success is always temporary. Bush's successor should of course steer away from the last administration -- that is a given. But he should also resist the too-easy temptation of letting the last administration shape the next one, if only by showing it what not to do. Instead, the next president should combine FDR's "bold, persistent experimentation" with Eisenhower's prudent handling of a nasty Asian war and Reagan's intoxicating optimism. Inauguration Day is still months away, but history suggests that today's storm clouds can part nearly as quickly as they formed -- given the right combination of luck, vision and endless adaptation.