President Bush's unusual appearance on"Meet the Press" yesterday underscored two important points about the coming election: Bush himself is likely to be the main issue and, despite the many advantages of incumbency, he is beginning the year in a defensive crouch.

His aggressive responses to moderator Tim Russert underscored both what his admirers and critics see in him - the resoluteness and the stubbornness - except this time he was answering questions that largely challenged his judgment, and the combativeness seemed strained.

"I'm a war president," Bush declared at one point."I make decisions here in the Oval Office in foreign policy matters with war on my mind. And again, I wish it wasn't true, but it is true. And the American people need to know they've got a president who sees the world the way it is. And I see dangers that exist, and it's important for us to deal with them."

Statements like those won Bush many admirers after the Sept. 11, 2001, terrorist attacks, but this time they were presented in the context of explaining a war he started because, he said at the time, there was"no doubt" that Iraqi leader Saddam Hussein had weapons of mass destruction.

Now, while Bush insisted his decisions were based on solid evidence, came about after full consideration of less-lethal options, and are still soundly justified, his very certitude seemed to suggest otherwise. The interview made clear that Bush is still absolutely sure of himself even as some around him, such as Secretary of State Colin Powell, acknowledged that lack of weapons of mass destruction would have changed the calculus on going to war.

Bush's current justification for the war is almost identical to his justification before the war, except he now stresses that Hussein had the" capacity to make a weapon" of mass destruction, rather than the actual weapons.

In fact, weapons inspector David Kay's interim report last fall alluded to"weapons of mass destruction-related activities" but made it clear that Hussein was far from being able to develop a nuclear weapon. The report quotes Iraqi scientists as discussing ways to make chemical and biological weapons, but offered no evidence yet of the agents that would be needed to make them.

Bush's justifications were probably strong enough to satisfy those disposed to support military action in the Middle East, but they seemed certain to unleash a round of questioning from skeptics.

Massachusetts Senator John F. Kerry, the winner of 10 Democratic primaries or caucuses, issued a statement calling on Bush to"take responsibility for his actions and set the record straight."

The fact that Bush chose to appear on"Meet the Press" signaled to analysts that the Democratic campaign was drawing blood.

"There's been a constellation of events, some of which Bush can control and some of which he can't, that have put him on the defensive," said Boston University historian Michael Corgan."The White House obviously feels they can't just sit back and wait until September to ramp up their campaign."

Among the events cited by Corgan - and covered in Russert's interview - were Kay's testimony that"we were all wrong" about weapons of mass destruction in Iraq; the insistence of Iraq's Shi'ite leaders on early elections, a potentially destabilizing move that jeopardizes Bush's promised changeover of power by June 30; criticism by many conservatives of the growing deficit; and slower-than-expected job creation.

Bush sought to lower expectations for a smooth road to democracy in Iraq, and expressed confidence in the economy.

When Russert confronted the president with a General Accounting Office report stating that rising debts would force the government either to cut half its discretionary spending by 2040 or institute a huge tax hike, Bush responded deftly: He portrayed his insistence on tax cuts as a sign of his empathy for the average person looking for a job.

Moments like those showed that Bush still carries an unusual ability to communicate his priorities in simple terms that register with average voters. It is an ability he will obviously put to use later in the campaign, when events may be more favorable.