Despite testimony from a host of current and former high-level government officials, it was the appearance of previously little known former counterterrorism official Richard Clarke that galvanized this week's hearings before the independent commission investigating the 2001 terrorist attacks. "By invading Iraq, the president of the United States has greatly undermined the war on terrorism," he said.

Mr. Clark's basic assertion was that the Bush administration paid too little attention to the threat posed by al-Qaida before the September 11 attacks and focused too much on Iraq afterward. The charges made in the hearing and in his new book, Against all Enemies, brought a counter-attack from Bush administration officials, though the president confined his response to a defense of his handling of the war on terrorism.

"We have been chasing down al-Qaida ever since they attacked us," he said. "We have captured or killed two-thirds of their known leaders and we are still pursuing them, and we will continue to pursue them so long as I am the president of the United States."

Public opinion polls suggest President Bush's main advantage in his re-election bid this year is the public's strong view of his handling of the war on terrorism, which is why the White House was quick to respond to Richard Clarke.

"Well, this subject goes right to the heart of the Bush presidency and he is running as a wartime leader," said Larry Sabato, a political analyst at the University of Virginia. "We are in a war, the war on terrorism, and Bush's chances in getting re-elected depend upon Americans signing off on his leadership in that war. He certainly is not going to get re-elected on the quality of the economy."

Scott McClellan

White House aides released previous statements from Mr. Clarke that praised the administration's approach to al-Qaida, and presidential spokesman Scott McClellan raised the possibility that Mr. Clarke had political motives for writing his book.

"Certainly, let us look at the politics of it," he said. "His best buddy is Rand Beers, who is the principal foreign policy advisor to Senator Kerry's campaign."

During his testimony before the 9-11 commission, Mr. Clarke said he wrote his book to tell the truth about his counterterrorism experiences in both the Bush and Clinton administrations. He also denied political motives.

"I am not working for the Kerry campaign,' he said. "Last time I had to declare my party loyalty, it was to vote in the Virginia primary for president of the United States in the year 2000 and I asked for a Republican ballot. So let me say here as I am under oath that I will not accept any position in the Kerry administration, should there be one."

In the face of the White House response, Democrats rallied to his defense, including Senate Democratic Leader Tom Daschle. "Instead of dealing with it factually, they have launched a shrill attack to destroy Mr. Clarke's credibility," he said.

Rutgers University political expert Ross Baker says just as Democrats are defending Richard Clarke, Republicans see it as essential to defend the president's record on the war on terrorism.

"I think the immediate impact has been considerable, judging from the ferocity of the response by people in the White House to the testimony by Richard Clarke," he said. "It is clear that they are extremely alarmed about this and have rallied to the president's side."

Despite the political firestorm resulting from the Clarke allegations, a number of analysts question how much of an impact the controversy will have when Americans vote for president in November.

"This has really not gripped the American public," said University of Virginia political expert Larry Sabato. "It has gripped the news media, but not the public. So, all in all, while this has not been helpful to Bush, in a few weeks time I do not know that anyone will focus on it."