By writing a memoir that slams the way President Bush handled Iraq and other matters, Scott McClellan has joined the parade of ex-White House aides cashing in at the expense of their former bosses.

Ever since James Fallows set a pattern three decades ago by exposing President Jimmy Carter’s penchant for micromanaging, top staffers from both parties have declined to delay their exposes until the end of their patrons’ presidencies.

It’s proved more lucrative for some than others; George Stephanopoulos’ account of infighting in the Clinton White House was the first step in transforming him from political operative to network journalist.

Whatever their motivation, though, these accounts are often quite revealing about what happened beyond the positive spin most White Houses like to present.

And reviews of McClellan’s book, “What Happened: Inside the Bush White House and Washington’s Culture of Deception,” seem to confirm some of the darkest depictions about Bush and his administration.

His account, though promptly and predictably questioned by the White House and Bush loyalists, gains credibility because the author had a long reputation both for being loyal to Bush and less caustic than his predecessor, Ari Fleischer.

McClellan’s depiction of Bush as “a man of personal charm, wit and enormous political skill” who showed a “lack of inquisitiveness” fits a conclusion reached by others who believe the president’s supreme self-confidence in his own instincts led him to ignore contrary views.

Also widely accepted is the contention that Bush managed the Iraq crisis “in a way that almost guaranteed that the use of force would become the only feasible option.” McClellan says the president sold the war by “propaganda,” rather than “the high level of candor and honesty so fundamentally needed to build and then sustain public support.”

McClellan also says, in an excerpt previously released, that top Bush advisers including Karl Rove and Scooter Libby misled him about their role in the leak of former CIA operative Valerie Plame’s identity.

The public White House reaction to the new book was one of puzzlement and sadness. “This is not the Scott we knew,” press secretary Dana Perino said, calling her predecessor “disgruntled about his experience at the White House.’

Former aides spoke more sharply. Rove told Fox News Channel that the book sounds like the work of “a left-wing blogger,” adding, “if he had these moral qualms, he should have spoken up about them.”

McClellan gives some indication of his motivation by noting he has “come to realize” that some things he said from the White House podium, while sincere, “were badly misguided.” He also indicates that, like former Bush strategist Matthew Dowd, he has come to see the Iraq effort as a mistake.

“History appears poised to confirm what most Americans today have decided: that the decision to invade Iraq was a strategic blunder,” he writes. And while it is impossible to know history’s ultimate verdict, he adds, “what I do know is that war should only be waged when necessary, and the Iraq war was not necessary.”

An easy explanation for such tell-all books – in which aides dump on the people and policies they served – is that a primary motivation is money, both the initial book contract and the substantial lecture fees it is likely to generate.

But a more charitable, and perhaps equally valid, explanation is that former aides, like the presidents they serve, are looking at the reputations they hope will enable them to keep playing a role in the public arena in their post-White House decades.

Given the fact that the Bush presidency is ending with such low approval ratings and so widespread a view among the public and historians that it has been a failure, it’s hardly surprising for a former aide to seek some distance from it.

Still, given McClellan’s long tenure in the Bush orbit, his comments seem unexpectedly pointed. And that gives them greater impact.