President Bush's credibility is the top issue in the presidential campaign, more important than jobs, the economy and health care, now that a former administration official says the president didn't take the terrorism threat seriously enough before Sept. 11, 2001, one-time Democratic presidential hopeful Howard Dean (search) said Wednesday.

Dean told a gathering of progressive Democrats that Bush failed to act on warnings from Richard Clarke (search), then Bush's counterterrorism chief, that Al Qaeda (search) posed a threat to the United States.

Dean, a former Vermont governor and harsh critic of the Iraq war, blamed Bush for the hundreds of U.S. soldiers killed and the thousands wounded in the Iraq war.

"That is the legacy of this president who did not tell the truth to the American people," he told about 150 people at the annual dinner for 21st Century Democrats (search), a political action committee that places activists on progressive campaigns.

Dean said he thought jobs, health insurance and economic security would be the biggest issues of the presidential election. But now, "the credibility of the president of the United States is the biggest issue of this race," he said.

The White House has dismissed Clarke's allegations as politically motivated and said Bush began putting in place a comprehensive plan to destroy Al Qaeda upon taking office in January 2001.

Dean also touted his new advocacy group, Democracy for America, and said it would partner with 21st Century Democrats to train people to knock on doors and make phone calls to encourage Democrats to run for office.

"If you haven't signed up, we want you," he said.

Democrats need to "focus their message in a laser-like way," he said, to oust the Bush administration.

"These are people who belong in Crawford, Texas, and not in the nation's capital," he said.

Dean, once the front-runner in the Democratic presidential race, ended his bid in February after failing to win any of the early nominating contests. Last week, he formally endorsed his former presidential rival, Massachusetts Sen. John Kerry.