It couldn’t last, the unlikely season of substance that seemed to dominate the landscape of national politics. It couldn’t — and it didn’t. In the past week, the seasons changed and, suddenly, we’re deep into the Silly Season. The Silly Season, in case you hadn’t noticed, is a time of bluster and buffoonery, speculation and spectacle (which is a pretty fair way to describe the reaction to retired Gen. Wesley K. Clark’s entry into the presidential race). Otherwise serious people do silly things, and otherwise silly events are taken seriously (prime example: this week’s announcement that former Sen. Carol Moseley Braun is running for the White House).

The Silly Season sometimes lasts longer than the hurricane season, often with similar results to the reputation of politicians and pundits who get caught in the unpredictable winds of autumn. This is turning out to be a particularly rich season for tropical cyclones, storm surges — and windy pronouncements. What’s needed in this atmosphere is an emergency preparedness kit for the silliness of the weeks ahead. So here are some of the latest received truths that probably aren’t true:

Gen. Clark is a stalking horse for Hillary Rodham Clinton and her secret plan to become president. This notion requires two leaps of faith. The first is that Hillary Clinton, elected to the Senate about five seconds ago, is ready to run for president next year. The second is that a general who, years before he contemplated the presidency, wouldn’t walk into the State Department without a fawning advance guard of crisp military attaches is selfless enough to run for president — and suffer the indignities of Iowa activists — for someone else.

The Clintons are backing Clark so as to keep their pal Terry McAuliffe in charge of the Democratic National Committee. The Silly Season doesn’t get any sillier than this. The McAuliffe conspiracy plan requires some unlikely elements, one of which is the idea that the Clintons are loyal to someone besides themselves. In any case, the leadership of the party apparatus, whether Republican or Democratic, almost always changes with the nomination of a presidential candidate. Which leads to the next item:

Rep. Richard Gephardt is making headway by arguing that he’d fire Atty. Gen. John Ashcroft in the first five seconds of his presidency. This is a beauty, proof of Abraham Lincoln’s view that politicians were “one long step removed from honest men.” Every president begins with a new slate and, once the confirmation procedure is completed, a new Cabinet. But this remark at least shows that Gephardt has been paying attention. The Missouri Democrat was 27 years old when Richard M. Nixon campaigned for president by saying he’d fire Lyndon Johnson’s attorney general, Ramsey Clark. This tactic was so effective that Lyndon Johnson eventually blamed Clark for Nixon’s triumph in 1968. (The poetic justice of injustice: Ramsey Clark later represented Slobodan Milosevic, the Yugoslav dictator whose reign of cruelty led to the war that brought Wesley Clark to prominence.)

Wesley Clark’s military credentials are so compelling that his presence on the Democratic ticket will inoculate the party against public suspicions that it is weak on defense. This is a plausible theory but not an unassailable one. Georgia’s Democrats thought the same thing about Sen. Max Cleland, who lost an arm and two legs in Vietnam and was a member of the Armed Services Committee. Then, in a bitter Senate contest last year, Rep. Saxby Chambliss aired a television ad that showed photographs of Cleland, Osama bin Laden and Saddam Hussein and attacked the incumbent for his record on homeland security. Cleland lost, providing a cautionary tale for Democrats who believe that a military background can protect a candidate in a tough race.

The Democratic race is now a death struggle between Clark and Howard Dean, last week’s media darling. How swiftly the wheel turns! When I typed my column last week, the smart people thought the contest was between Dean and Sen. John F. Kerry of Massachusetts. Things sure change quickly around here.

But the contours of the 2004 presidential race really haven’t changed much at all. The broader theme remains the same: Can any of the relatively unknown Democrats emerge from a crowded field with sufficient credibility to challenge a sitting president at a time of global threats? The factors in the calculus remain the same as well: the continued threat of terrorism at home and abroad, the risks of American engagement in the Middle East and Central Asia, and the uncertainties of the economy.

The late entrant gets the prize. Nine of the 10 Democrats running for president think this theory is rubbish, and in truth only one late entrant in the past half-century has won his party’s nomination. He was Hubert H. Humphrey, and his entry came in the spring of 1968, after President Johnson surprised the nation by announcing he wouldn’t seek another term. The obstacles aren’t so much the usual — the financial lead the others have built up, the fact that activists have already signed up with competitors — but the essential. Clark’s nine opponents have been at this game for some time, and for the most part they know what they think. In the past week, Clark has issued three conflicting statements on an important issue, and it wasn’t a complicated question like how the 1996 farm bill affected income support programs for grain sorghum, but one that a general (and television talking head) might be expected to have mastered: Was the Iraq war a good idea?

All of which suggests that the only safe conclusion in the stormy 2004 campaign might be this: Like the campaign of Wesley Clark, this election is a work in progress.

David Shribman is a columnist for the Pittsburgh Post-Gazette.