John Kerry said Saturday the White House is committing character assassination with its treatment of former counterterror chief Richard Clarke to avoid responding to questions about national security.
Kerry also said Condoleezza Rice, President Bush's national security adviser, should testify in public before the commission investigating the Sept. 11, 2001, terror attacks.
"If Condoleezza Rice can find time to do `60 Minutes' on television before the American people, she ought to find 60 minutes to speak to the commission under oath," Kerry told reporters. "We're talking about the security of our country."
The White House has said that presidential staff advisers, such as Rice, cannot testify publicly before congressional bodies. The bipartisan, independent commission was created in 2002 by congressional legislation and Bush's signature.
Rice has been interviewed privately by commission members.
Bush campaign spokeswoman Nicolle Devenish said Kerry and other Democrats are trying to politicize the work of the commission.
"John Kerry seeks to distract Americans from his own failed ideas for protecting America from future attacks," she said in a statement. "John Kerry's backward-looking approach would return us to the failed policies of treating terror as a law-enforcement matter."
Kerry said the constitutional separation of powers could be protected despite the White House's objections.
"Certainly we can find a way to respect executive privilege, not to have it be an opening to the door, but nevertheless to accomplish America's needs to protect the security of our country," he said.
A poll released Saturday shows two-thirds of Americans say Clarke's testimony hasn't affected their view of the president. But public views supporting Bush's handling of terrorism have dipped from 65 percent to 57 percent in the last month, according to the Newsweek poll.
Half those surveyed in the poll after Clarke's testimony Wednesday said they thought he was acting for political and personal reasons, while a quarter said they feel he's acting as a dedicated public servant.
While 65 percent said Clarke's testimony has not affected their views of Bush, 17 percent said it made them view him less favorably and 10 percent said more favorably.
Two-thirds said the Clinton administration did not take the threat of terror seriously enough, while six in 10 said the Bush administration has taken the threat as seriously as it should.
The poll found the presidential race between Bush and Democrat John Kerry tied and found Bush's job approval was 49 percent.
The poll of 1,002 adults was taken Thursday and Friday and has a margin of sampling error of plus or minus 3 percentage points.
On Clarke, Kerry said: "Every time somebody comes up and says something that this White House doesn't like, they don't answer the questions about it or show you the truth about it. They go into character assassination mode."
Besides Clarke, Kerry cited the examples of former Treasury Secretary Paul O'Neill and Medicare accountant Richard Foster.
"It is entirely inappropriate and almost hysterical of the White House to engage in this massive character assassination," Kerry said later in an interview with Kansas City television station KMBC.
O'Neill was fired as Treasury secretary in December 2002 after publicly questioning the need for additional tax cuts, a core campaign issue for Bush. Foster said he was prohibited by his superiors from sharing with Congress a much higher but more accurate cost estimate for the administration's Medicare program.
Kerry said until the commission completes its report, he will comment neither on Clarke's testimony nor on whether Bush did enough to protect Americans before the attacks. Kerry, who spent much of the past week on vacation in Idaho, said he had not heard or read any of the testimony before the commission.
He nevertheless criticized the administration for having "stonewalled" the investigation. Bush originally opposed the panel's creation, then opposed its request for a two-month extension of its work, but eventually relented on both counts.