FULTON, Mo. -- Vice President Dick Cheney, stepping forcefully into his role as John Kerry's chief critic, questioned on Monday whether the Democrat is fit to serve as president in a time of war. Democrats said the tactic is a sign of desperation.

"It's time for Dick Cheney to call off the Republican attack dogs," said Democratic National Committee chairman Terry McAuliffe.

Cheney is the White House's designated attacker -- held in reserve for the toughest times and sharpest messages. When the vice president goes negative, it usually means the White House is braced for trouble.

This week is no exception:

President Bush and Cheney are scheduled to testify jointly Thursday before the Sept. 11, 2001, commission investigating whether more could have been done to prevent the worst terrorist strikes on U.S. soil.

Saturday is the one-year anniversary of the speech Bush delivered aboard an aircraft carrier celebrating the fall of Baghdad. The address, given under a "Mission Accomplished" banner, has become fodder for Democrats who question the war and argue that it's far from over.

The Supreme Court will consider today whether Cheney must release internal documents detailing the membership of a task force that met privately to help Bush develop an energy plan.

In March, amid rumors that he may be bumped from the ticket, Cheney resurfaced from a long stretch outside the public eye to question Kerry's fitness to be president. "The senator from Massachusetts has given us ample doubts about his judgment," Cheney said at the time.

That speech was part of a larger administration effort to undermine Kerry as the one-year anniversary of the start of the Iraq war approached -- a milestone met with violence and voters' doubts.

Cheney returned to the theme Monday, breaking little new ground while repeating the best lines from his March speech. "The senator from Massachusetts has given us ample grounds to doubt the judgment and the attitude he brings to bear on vital issues of national security," Cheney said at Westminster College, where Winston Churchill in 1946 warned against the "Iron Curtain" of communism.

Kerry has wavered on his commitment to ousting Saddam Hussein as well as his view of the Persian Gulf War coalition built by Bush's father in the 1990s, Cheney said -- backing up his assertions with Kerry's own statements.

He mocked Kerry's habit of producing confusing or contradictory explanations of his own foreign policies, such as when the Democrat said he voted for -- and against -- an $87 billion aid package for Iraq and Afghanistan. Kerry has voted to cut U.S. intelligence spending and consistently underestimates the threat of terrorism, Cheney added.

Faced with voter unease about Iraq, the White House's offensive also includes a $10 million television ad campaign accusing Kerry of opposing vital weapons.

The Kerry campaign responded with a fact sheet detailing the vice president's record as defense secretary under Bush's father, including a long list of proposed weapons cuts sought by Cheney. It quotes Cheney seeking defense cuts during the Cold War.

The Bush campaign maintains that Cheney's positions reflected the availability of a "peace dividend" after the Soviet Union collapsed. Kerry says he supported large increases in defense spending and sought only to eliminate unnecessary programs.

Both men are paying the price for positions taken long ago, many predating Bush's relatively brief political career.

While Bush has Cheney, Kerry has no No. 2. Until he selects a running mate, the four-term Massachusetts senator must rely on second-tier surrogates such as McAuliffe.

"The American people have better things to do with their time than listen to more misleading attacks from a man who has been misleading them from the day he took office," the Democratic chairman said in Washington.

The quick response from Kerry's camp reflects a concern that voters are beginning to view the Democrat in terms cast by Bush: a flip-flopping, tax-raising opportunist.

Later this week, Kerry plans to criticize Cheney's actions on the energy task force and the vice president's ties to Halliburton Co., a major U.S. contractor in Iraq.

The Democrat, whom polls show is in a tight race with Bush, embarked on a bus tour through several states hard hit by the economy. In West Virginia, Kerry was greeted by a Bush newspaper ad criticizing the Democrat's position on coal, the state's treasure.

As for Cheney, polls show him enormously popular among dedicated Republicans but with a high disapproval rating overall. Bush and his political team have quashed rumors that Cheney will be dumped from the ticket.

Cheney is not the first vice president to lead White House criticism of a rival, but he's become an unusually big target.

"What is unique about Cheney is not so much his being used to attack," said Ron Klain, who worked for former Vice President Al Gore in the Clinton White House, "but how much of what is being attacked in the administration stems from him."

Bill Kristol, who worked for former Vice President Dan Quayle, said Democrats are foolish to target Cheney instead of Bush. "Damaging the vice president is of very little importance, ultimately," said Kristol, editor of The Weekly Standard.