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When details began emerging in 2003 to suggest that senior administration officials may have leaked the name of CIA agent Valerie Plame (search), White House spokesman Scott McClellan told reporters that anyone in the White House found to be involved "would no longer be in this administration."

McClellan also denied, based on all "available information," that White House senior adviser Karl Rove (search) and other high-level administration officials were involved in the leak, calling the suggestion "ridiculous."

Fast forward to July 11, 2005. McClellan finds himself on the hot seat in front of a hostile White House press corps, days after it is revealed that Rove told Time magazine reporter Matt Cooper that the unnamed wife of Ambassador Joe Wilson had played a role in sending Wilson to Niger in 2002 to investigate whether Saddam Hussein was attempting to buy enriched uranium from the African nation.

By July 18, President Bush appeared to be qualifying McClellan's earlier remarks that he would fire anyone involved with leaking classified information, telling reporters, "If someone committed a crime, they will no longer be in my administration."

By this time, McClellan, who is no longer answering questions about the leak investigation, had left himself open, according to reporters, to attacks about what seem to be shifting positions on a volatile, yet complicated story.

McClellan's critics have suggested that his credibility with the press corps was severely damaged on this story from nearly the beginning because almost immediately the CIA asked for a Justice Department probe into whether White House officials were guilty of leaking a covert agent's name to reporters. McClellan's earlier remarks also appeared to jumpstart the record that Bush's desire was to see fired anyone involved in the leak.

But claiming an effort has been made to pull a bait and switch on the press is a serious charge to make against any spokesman, said Will Haynie, a columnist and former spokesman for Rep. Charles Taylor, R-N.C. A spokesman's being deliberately misleading or disingenuous hurts him and his boss, and most are careful not to cross that line.

"If you start covering tracks or being evasive, you can lose your credibility with both the public and the press," Haynie said. "But you are under tremendous pressure."

Press secretaries are acutely aware that every word will be dissected by reporters and could get the boss in trouble, which is why they rarely go out on a limb. Caution is the key word, experts say, especially for a White House spokesman who fronts an administration that is the target of an independent prosecutor and media frenzy.

Former Capitol Hill spokesmen, reporters and public affairs specialists told FOXNews.com that McClellan is the latest in a long line of embattled front men and women who have found themselves in a difficult position — somewhere in the middle of informing the press, protecting the boss and preserving one's own credibility.

"The spokesman in my view has the toughest job in the White House," said Peter Roussel, former deputy press spokesman for President Ronald Reagan. "You have to be responsible to not one but two entities — the administration you are representing and also to the press corps. Each day a spokesman has to go out there and serve both of those."

Terry Madonna, director of the Center for Politics and Public Affairs at Franklin & Marshall College in Pennsylvania, said it requires an extraordinary personality to fulfill effectively the job of White House spokesperson.

"They're always in the hot seat. Who would want that job?" Madonna said, noting that most official spokesmen are "very cool and their demeanor is very calm, it's unflappable."

While McClellan's critics have questioned his credibility because of what appears to be different positions on the leak probe, senior Washington Times White House correspondent Bill Sammon said the seemingly mild-mannered McClellan need not be concerned.

"I think the press is parsing Mr. McClellan's and Mr. Bush's words," said Sammon, also a FOX News Channel analyst, who added that put into context, Bush and McClellan's statements have been pretty consistent. "If you look at what the words mean, there really isn’t a disconnect."

While in the past, press secretaries have "walked the high dive" with less information than they should have on a hot-button issue, Sammon said he believes that McClellan truly speaks with the president's voice, is "in the loop" as far as the controversial topics go and has not misrepresented Bush's position on this or any other issue.

"Does he give out a lot of information? No. Is he notoriously bland on a lot of issues because he has to be? Yes. But is he disingenuous? No," Sammon said, noting that most of Bush's press secretaries have been notably cautious and reluctant to make news.

One incident in the Bush White House, in which former spokesman Ari Fleischer was forced to clarify some off-the-cuff remarks he made about Iraqi dictator Saddam Hussein (search), did cause some embarrassment.

In an October 2002 press briefing, Fleischer snapped that "one bullet" in Hussein's head would be cheaper than a war to topple the Iraqi dictator — clearly not the official line of the White House at the time.

According to reports, Fleischer, who resigned in 2003 on good terms with Bush, also privately accused superiors of passing bad information to the press office while the senior staff would quietly point the finger back to Fleischer.

Credibility is key to any successful spokesperson, said Roussel, which is why most presidential press secretaries wouldn’t be caught dead lying to the press.

"The first time you tarnish your credibility by misleading the people and lying, you might as well pack up your Adidas and hoof it out of there," he said.

Some administration officials of the past certainly have altered their position in order to ease their conscience and maintain credibility with the press.

During the 1998 scandal, President Bill Clinton was forced to admit that he did have an affair with the then-24-year-old intern Monica Lewinsky after lying to the American public that he "did not have sexual relations with that woman, Miss Lewinsky." Several top aides were forced to acknowledge they had been lied to, too.

Democratic strategist Paul Begala, who as a White House adviser had vociferously defended Clinton on the talk show circuit, told The Washington Post in 1998 that he believed Clinton was innocent of the affair and was "crushed" to find out that Clinton had lied to him and allowed Begala to compromise his own integrity.

"I was very angry, I was very disappointed. I didn’t want to have to say that on television," Begala is quoted as saying.

White House spokesman Mike McCurry, who apparently did not know Clinton was lying, was nonetheless careful not to vouch for Clinton personally. Instead, McCurry repeated Clinton's denials up to the explosive Lewinsky admission. He had already handed in his resignation when the new broke on Aug. 17, 1998.

"You obviously wrestle with this," he told The Post's Howard Kurtz. "A certain amount of loyalty goes to the person who hired you and put you in a position of trust. But you realize you have a larger purpose that goes beyond the individual you're working for. You've not an obligation to a larger universe — and American public that pays your salary. You could do a great amount of damage if you're putting out false information."

Sometimes the act of keeping a spokesman in the dark is done "deliberately," both in the corporate world and in high-stakes politics, said Suzanne Bates, a former television news anchor who now runs her own Boston public affairs consulting firm where she trains business leaders and politicians. The practice is generally not good sense, she said, adding that she did not want to suggest that was the case in the White House today.

"If the people at the top appreciate the value of the spokesperson's role, and they trust the spokesperson and they aren't trying to hide anything — they usually keep the spokesperson in the loop," Bates said.