THE PRESIDENTIAL election debate is now focused on the most important issue facing the country, which is the war against Islamic extremism and terrorism that began three years ago this week. So far, however, the substance of that debate has been disappointing. President Bush and Democratic challenger John F. Kerry have each tried to make the case for himself as the most credible commander in chief, but they have done so mainly by flaunting past experience, in the case of Mr. Kerry, or by questioning his opponent's steadfastness, in Mr. Bush's case. What neither has done so far is convincingly address the specific and critical challenges the United States faces in Afghanistan and Iraq, or those that lie just over the horizon: in Iran, in North Korea, in the emergence of new terrorist networks. Yet it is there -- and not on each man's personal history during the Vietnam War, or the wording of their predictions of eventual victory -- that the real distinctions between them need to be made.

In his speech to the Republican National Convention on Thursday, Mr. Bush articulated a broader, more ambitious -- and, we'd say, more compelling -- vision than has Mr. Kerry of the stakes of this conflict and the means needed to win it. Once again the president passionately committed himself "to advance liberty in the broader Middle East, because freedom will bring a future of hope." Mr. Kerry has been largely silent, and occasionally skeptical, about such an aim. Yet it is simply not true, as Mr. Bush, Vice President Cheney, and countless other Republican spokesmen have contended, that Mr. Kerry does not consider the United States to be at war, or is unwilling or unqualified to fight. Contrary to the malignant and men- dacious convention speech of Sen. Zell Miller (D-Ga.), Mr. Kerry has said repeatedly that he will not give other nations a veto over U.S. military action. He has said he will consider preemption if necessary and has called for a considerable expansion of the U.S. Army. The Republican effort to cast doubt on these posi- tions by citing 30-year-old interviews with college newspapers, or decade-old votes stripped of their legislative and historical context, is scurrilous.

It is also unnecessary. Mr. Bush might well distinguish himself from Mr. Kerry by debating him on the critical question of Iraq -- where the Democrat's position is indeed wobbly. Last week Mr. Kerry laid out a strong and mostly convincing critique of all that Mr. Bush had done wrong in Iraq, from failing to deploy enough troops to refusing to internationalize the occupation. None of these failings were acknowledged in Mr. Bush's account. But Mr. Kerry's own plan boils down to enlisting allies who can "reduce the cost" to American taxpayers and soldiers -- an unlikely prospect. He says he will "get the job done and bring our troops home," perhaps many of them within six months. But what is "the job?" Mr. Kerry is no more clear about this than he has been about whether he would, in the end, have ordered an invasion of Iraq had he been president.

Mr. Bush, unfortunately, is also keen to dodge the realities of the war. Other than a vague promise to see Iraq "on the path of stability and democracy," he has offered voters no hint of a plan for countering the violence that continues to cost one or two American lives a day. He says he will stand up to every threat, but he says nothing about Fallujah, the western Iraqi city where an extremist Islamic regime backed by foreign terrorists appears to be taking root, as U.S. Marines stand by and watch.

The president could also challenge Mr. Kerry on Iran -- with which running mate John Edwards has proposed an improbable "great bargain" -- or North Korea, where Mr. Kerry similarly advocates bilateral negotiations that already once failed. But Mr. Bush has no coherent strategy of his own for these two near-nuclear states -- and so they went unmentioned in a convention speech that tackled health insurance for employees of small businesses and funding for community colleges. Such omissions leave voters to wrestle with the questions of character the candidates seem to prefer: the sobriety and experience of Mr. Kerry vs. the modesty of his foreign policy goals; the passion of Mr. Bush for the "use of American strength to advance freedom," vs. the recklessness and incompetence that may come with it. It's not a slam-dunk choice, but if the candidates can be induced to debate the real issues before them in the coming two months, it will be easier.