WASHINGTON - President Bush portrays his position on Iraq as steady and unwavering as he represents Sen. John Kerry's stance as ambiguous and vacillating.

"Mixed signals are the wrong signals,'' Bush said last week during a campaign stop in Bangor, Maine. "I will continue to lead with clarity, and when I say something, I'll mean what I say.''

Yet, heading into the first presidential debate Thursday, which will focus on foreign affairs, there is much in the public record to suggest that Bush's words on Iraq have evolved -- or, in the parlance his campaign often uses to describe Kerry, flip-flopped.

An examination of more than 150 of Bush's speeches, radio addresses and responses to reporters' questions reveal a steady progression of language, mostly to reflect changing circumstances such as the failure to discover weapons of mass destruction, the lack of ties between Iraq and the al Qaeda terrorist network and the growing violence of Iraqi insurgents.

A war that was waged principally to overthrow a dictator who possessed "some of the most lethal weapons ever devised'' has evolved into a mission to rid Iraq of its "weapons-making capabilities'' and to offer democracy and freedom to its 25 million residents.

The president no longer expounds upon deposed Iraqi strongman Saddam Hussein's connections with al Qaeda, rarely mentions the rape and torture rooms or the illicit weapons factories that he once warned posed a direct threat to the United States.

In the fall of 2002, as Bush sought congressional support for the use of force, he described the vote as a sign of solidarity that would strengthen his ability to keep the peace. Today, his aides describe it unambiguously as a vote to go to war.

Whether such shifts constitute a reasonable evolution of language to reflect the progression of war, or an about-face to justify unmet expectations, is a subjective judgment tinged by partisan prejudice.

Yet a close look at the record makes it difficult to support Bush campaign chairman Ken Mehlman's description of the upcoming debate as a "square-off between resolve and optimism versus vacillation and defeatism.''

A careful reading of Bush's statements on Iraq reveals many instances of consistency, just as The Chronicle's examination of Kerry's words found consistency in the Democratic challenger's statements. Over and over, Bush stated that the tragedy of Sept. 11, 2001, changed the way Americans -- including the commander in chief -- viewed the threat of terrorism and lowered the threshold of risk Americans were willing to accept.

"Saddam Hussein's regime is a grave and gathering danger. To suggest otherwise is to hope against the evidence. To assume this regime's good faith is to bet the lives of millions and the peace of the world in a reckless gamble. And this is a risk we must not take,'' Bush said in a well-received speech before the U.N. General Assembly on Sept 12, 2002.

Bush echoed those words earlier this month as he accepted his party's nomination for president a few miles away, at Madison Square Garden in New York:

"Do I forget the lessons of September the 11th and take the word of a madman, or do I take action to defend our country? Faced with that choice, I will defend America every time.''

Yet the more specific explanation of a mission that has cost more than 1, 000 American lives, thousands of Iraqi lives and well over $100 billion has undergone a transformation.

Prior to the March 2003 invasion of Iraq, Bush focused on weapons of mass destruction and stated the U.S. goal in straightforward terms.

"Should we have to go in, our mission is very clear: disarmament. And in order to disarm, it would mean regime change,'' Bush said at a news conference two weeks before he took the nation to war.

"And our mission won't change,'' Bush continued. "Our mission is precisely what I just stated.''

Six weeks later, speaking to workers at an Army tank plant in Ohio, the goal seemed to expand.

"Our mission -- besides removing the regime that threatened us, besides ending a place where the terrorists could find a friend, besides getting rid of weapons of mass destruction -- our mission has been to bring humanitarian aid and restore basic services and put this country, Iraq, on the road to self- government.''

Last month, speaking to supporters at a campaign event in Wisconsin, Bush put it more plainly: "The goal in Iraq and Afghanistan is for there to be democratic and free countries who are allies in the war on terror. That's the goal.''

In the course of the campaign, such shifts have been characterized by Bush's opponents as lies.

"He failed to tell the truth about the rationale for going to war,'' Kerry said during a speech at New York University last week in which he said Bush has offered 23 different rationales for going to war. "If his purpose was to confuse and mislead the American people, he succeeded.''

The count comes from a study conducted by an honors thesis written by a University of Illinois student, which actually attributed 19 rationales -- none mutually exclusive -- to Bush and four others to members of his administration.

Most of the rationales were on the table from the beginning. What changed was the emphasis.

Bush voiced no doubt from the beginning that Hussein possessed chemical, biological and potentially nuclear weapons.

"Year after year, Saddam Hussein has gone to elaborate lengths, spent enormous sums, taken great risks, to build and keep weapons of mass destruction,'' Bush said in his State of the Union address in January 2003.

By the following year, after no such weapons had been discovered and evidence suggested that much of the intelligence was wrong, Bush had toned down such talk and begun to speak of the "threat'' of Hussein developing such weapons.

In his State of the Union address last January, Bush spoke of Hussein's "mass destruction-related program activities."

"Look, there is no doubt that Saddam Husein was a dangerous person,'' the president told ABC's Diane Sawyer in an interview several weeks before that speech. "And there's no doubt we had a body of evidence providing that. And there is no doubt that the president must act, after 9/11, to make America a more secure country.''

Sawyer asked the president about the distinction between the "hard fact that there were weapons of mass destruction as opposed to the possibility that he could move to acquire those weapons.''

"So what's the difference?'' Bush responded. "The possibility that he could acquire weapons, if he were to acquire weapons, he would be the danger.''

"What would it take to convince you he didn't have weapons of mass destruction,'' Sawyer persisted.

"Saddam Hussein was a threat,'' Bush responded. "And the fact that he is gone means America is a safer country.''

In the months since, Bush has changed his standard speech to reflect that failure to discover the weapons.

"Although we have not found stockpiles of weapons of mass destruction, we were right to go into Iraq,'' Bush said in July in Tennessee. "We removed a declared enemy of America who had the capability of producing weapons of mass murder and could have passed that capability to terrorists bent on acquiring them. In the world after September the 11th, that was a risk we could not afford to take.''

There are a few instances where the president's words contradict developments or his previous statements.

On March 6, 2003, for example, Bush insisted during a prime-time news conference that he would offer a resolution before the United Nations calling for the use of force against Iraq even if other nations threatened to veto it.

"No matter what the whip count is, we're calling for the vote,'' Bush said.

A few days later, after it became apparent that the measure would not only be vetoed but might fail to win a majority of the Security Council, the Bush administration dropped its demand for a vote.

The president also said last month on NBC's "Today Show'' that "I don't think you can win'' the war on terrorism, explaining instead that the nation could greatly minimize the likelihood of terrorist attacks. The comment came after months of asserting the United States was winning, and would ultimately triumph, in its war on terror. The statement appeared to be little more than an inelegant way of adding nuance to his explanation, and the president quickly retreated from the words the following day.

Some statements now look off-base after developments in Iraq, such as Bush's response in the first days of the war after learning that Iraqis may have captured some Americans.

"I do know that we expect them to be treated humanely, just like we'll treat any prisoners of theirs that we capture humanely,'' Bush said, many months before American soldiers committed the atrocities at the Abu Ghraib prison.

Sept. 12, 2002 - Speech before the U.N. General Assembly

"Saddam Hussein's regime is a grave and gathering danger. To suggest otherwise is to hope against the evidence. To assume this regime's good faith is to bet the lives of millions and the peace of the world in a reckless gamble. And this is a risk we must not take.''

Sept. 19, 2002 - Response to a reporter's question

"If you want to keep the peace, you've got to have the authorization to use force. ... This is a chance for Congress to indicate support. It's a chance for Congress to say, we support the administration's ability to keep the peace. That's what this is all about.''

Oct. 7, 2002 - Speech before the Veterans of Foreign Wars, Cincinnati

"Saddam Hussein is harboring terrorists and the instruments of terror, the instruments of mass death and destruction. ... Knowing these realities, American must not ignore the threat gathering against us. Facing clear evidence of peril, we cannot wait for the final proof -- the smoking gun -- that could come in the form of a mushroom cloud.''

March 6, 2003 - News conference

"Should we have to go in, our mission is very clear: disarmament. And in order to disarm, it would mean regime change.''

March 17, 2003 - Address to nation (two days before invasion)

"Intelligence gathered by this and other governments leaves no doubt that the Iraq regime continues to possess and conceal some of the most lethal weapons ever devised. The danger is clear: Using chemical, biological or, one day, nuclear weapons obtained with the help of Iraq, the terrorists could fulfill their stated ambitions and kill thousands or hundreds of thousands of innocent people in our country or any other.''

May 1, 2003 - Aboard the aircraft carrier Abraham Lincoln

"Major combat operations in Iraq have ended. In the battle of Iraq, the United States and our allies have prevailed. ... The battle of Iraq is one victory in a war on terror that began on September the 11, 2001 -- and still goes on."

Nov. 11, 2003 - Veterans Day address

"Our mission in Iraq and Afghanistan is clear to our service members -- and clear to our enemies. Our men and women are fighting to secure the freedom of more than 50 million people who recently lived under two of the cruelest dictatorships on earth. Our men and women are fighting to help democracy and peace and justice rise in a troubled and violent region. Our men and women are fighting terrorist enemies thousands of miles away in the heart and center of their power, so that we do not face those enemies in the heart of America.''

Aug. 16, 2004 - Speech to the Veterans of Foreign Wars, Cincinnati

"Even though we did not find the stockpiles that we thought we would find, Saddam Hussein had the capability to make weapons of mass destruction, and he could have passed that capability on to our enemy, to the terrorists. It is not a risk after September the 11th that we could afford to take. Knowing what I know today, I would have taken the same action."