WASHINGTON — A former White House Press Secretary, Scott McClellan, defended his bombshell book about the Bush administration today, saying he didn’t speak up against the overselling of war in Iraq at the time because he, like other Americans, gave the president the benefit of the doubt.

“My beliefs were different then. I believed the president when he talked about the grave and gathering danger from Iraq,” Mr. McClellan, who was deputy press secretary during the lead-up to the war, told NBC’s “Today” show.

RELATED: Where McClellan Went Wrong.

Mr. McClellan, a longtime loyalist who worked for Mr. Bush when he was Texas governor, said his initial misgivings about a rush to war were offset by his affection for the president and respect for his foreign policy advisers. It was easy to believe, he said, because the president wasn’t consciously trying to inflate the threat of Iraq unleashing weapons of mass destruction.

“He came to convince himself of that,” Mr. McClellan said of Mr. Bush.

In hindsight, Mr. McClellan views the war as a mistake by a president swept up by his own propaganda and a grand plan of seeding democracy in the Middle East by overturning Saddam Hussein’s regime.

Mr. McClellan says Mr. Bush and his aides became so wrapped up in trying to shape the story to their political advantage that they ignored facts that didn’t fit the picture. He blames it on a “permanent campaign culture” that pervades Washington.

Mr. Bush began his presidency intending to change that culture, but instead got caught up in it, Mr. McClellan said.

“I’m disappointed that things didn’t turn out the way we all hoped they would turn out,” he said. “We all had high hopes coming in.”

Mr. McClellan said he grew “increasingly dismayed and disillusioned” during his final year as White House press secretary, and pinpointed the CIA leak case — and what it revealed about Mr. Bush’s role in releasing classified information about Iraq to the press — as his tipping point. Mr. McClellan was White House press secretary from May 2003 to April 2006.

Mr. McClellan said he hoped his book would help change the culture that has turned governing into a never-ending campaign, and said that was why he was willing to weather the storm of anger it would bring.

As the book — “What Happened: Inside the Bush White House and Washington’s Culture of Deception” —vaulted to No. 1 on Amazon.com’s best-seller list yesterday, Republican critics dismissed him as a turncoat, a sellout and a disgruntled former employee. The White House called the book puzzling and sad.

A former White House counselor, Dan Bartlett, offered an immediate rebuke to Mr. McClellan’s interview and his allegations of pro-war propaganda.

“I would not personally participate in a process in which we are misleading the American people, and that’s the part that I think is hurting so many of his former colleagues,” Mr. Bartlett said, also on speaking on “Today.” “To think that he is making such a striking allegation against his former colleagues, to me, is beyond the pale.”

Speaking earlier today to reporters in Sweden, Secretary of State Rice also rejected Mr. McClellan’s allegations that the Bush administration misled the American public into war.

Ms. Rice would not comment specifically on charges in the book, but said Mr. Bush was honest and forthright about the reasons for the war. She also said she remained convinced that toppling Saddam was right and necessary.

“The president was very clear about the reasons for going to war,” she told reporters in Stockholm, where she is attending an international conference on Iraq.

Mr. McClellan writes that Ms. Rice, who was national security adviser earlier in Mr. Bush’s presidency, “was more interested in figuring out where the president stood and just carrying out his wishes while expending only cursory effort on helping him understand all the considerations and potential consequences” of war.

Mr. McClellan identified the CIA leak case as the low point of his job.

He was ordered to say from the press room podium that two White House aides, Karl Rove and I. Lewis “Scooter” Libby, were not involved in leaking a CIA operative’s identity, Valerie Plame, to the press. Later a criminal investigation revealed that they were.

“I blame myself for putting myself in the position of going to the podium and passing along information I didn’t know was false, but later learned that it was,” Mr. McClellan said.

And Mr. McClellan recalled a day in April 2006, when the unfolding perjury case against Mr. Libby revealed that the president had secretly declassified portions of a 2002 intelligence report about Iraq’s weapons capabilities to help his aides deflect criticism that his case for war was weak. Some of the most high-profile criticism was coming from Ms. Plame’s husband, a former ambassador, Joseph Wilson.

The president was leaving an event in North Carolina, Mr. McClellan recalled, and as they walked to Air Force One a reporter yelled out a question: Had the president, who had repeatedly condemned the selective release of secret intelligence information, enabled Scooter Libby to leak classified information to The New York Times to bolster the administration’s arguments for war?

Mr. McClellan took the question to the president, telling Mr. Bush: “He’s saying you yourself were the one that authorized the leaking of this information.”

“And he said, ‘Yeah, I did.’ And I was kind of taken aback,” Mr. McClellan said.

“For me I came to the decision that at that point I needed to look for a way to move on, because it had undermined, I think, a lot of what we had said.”