John Kerry is running neck and neck with President Bush. But there is a key issue on which voters still give Bush the edge.

It’s a question that is crucial in a campaign where foreign policy will be unusually important: Which candidate can best protect the American people from terrorists?

The Sept. 11 commission report says both the Clinton and Bush administrations did a poor job in combating Islamic terrorism. According to a recent Washington Post poll, only 46 percent of Americans think the country is winning the war on terrorism.

Yet the same poll finds that 51 percent of the public trusts Bush more than Kerry to deal with the fight against terrorism to 42 percent for the Democratic candidate. Fifty-five percent approve of the way Bush is handling the anti-terror campaign.

The figures for Bush are quite stunning given the continuing instability in Iraq and the undimmed terrorist threat. Not only did the Iraq war have no impact on curbing al-Qaida, but it also sidetracked critical resources. And it has created a serious new terrorist threat inside Iraq’s borders.

In sharp contrast to the president’s position, the Sept. 11 panel did not consider the invasion of Iraq to be part of the war on terrorism. In fact, the panel said that if Iraq becomes a failed state, it could become a “breeding grounds for attacks against Americans at home.”

Nor has Iraq provided the impetus that the administration predicted for democratic reform in the Arab world. Far from it. An unstable Iraq – and minimal U.S. involvement on the Israel-Palestinian issue – have isolated Arab liberals and dramatically increased hostility toward an America that is now widely considered anti-Muslim.

So why is Bush still favored over Kerry to lead the antiterrorist struggle? Perhaps in part because more than 40 percent of Americans still believe Iraq collaborated with al-Qaida and had a role in terrorist attacks.

Senior administration officials have repeatedly played up supposed ties between Iraq and al-Qaida. Yet the Sept. 11 panel, as well as the Senate Select Intelligence Committee report, found there was no “operational relationship” between the two and that nothing came of some infrequent contacts.

So misconceptions about Iraq may play a role. But something else has to be at play in producing these numbers. Clearly, John Kerry still hasn’t persuaded enough Americans that he would feel comfortable with projecting American power.

Many Americans still don’t feel they know enough about him, and he does project a confusing image. He’s a Vietnam War hero who voted against the first Gulf War and for the second. He nixed postwar reconstruction aid, but would have U.S. troops stay on there until that country is stable.

Kerry needs to clarify his foreign policy persona. He has put forward some good ideas to reinforce the antiterrorist fight, including a serious energy policy aimed at freeing us from dependence on Mideast oil. Hallelujah!

He would lead a worldwide effort to “lock up and safeguard nuclear weapons material so terrorists can never acquire it.” This includes a much more serious effort than made by the Bush administration to safeguard Russia’s vast supply of nuclear weapons and materiel and prevent any of it from being stolen. Black market salesmen of nuclear materiel or know-how (think Pakistan’s A.Q. Khan) are more likely sources for terrorists than was Iraq.

And of course, Kerry famously wants to revive the U.S. alliances that have been battered by Bush unilateralism, like NATO. The senator believes deeply that he could get more cooperation – and more troops for Afghanistan and Iraq – with a different approach.

Perhaps the Democrat is overdoing it, indulging, as the Economist noted dryly, in “an orgy of multilateralism” toward allies who would fail to deliver even to a President Kerry.

Yet the Bush team so unnecessarily alienated so many countries that the United States got stiffed when it needed help in Iraq. A corrective is definitely needed.

Even the administration, after rattling sabers at North Korea and Iran, found it had to turn to allies and diplomacy in an effort to curb their nuclear programs.

Perhaps people hesitate about Kerry because they aren’t sure what he would do if multilateralism failed. What if Iran insisted on building nuclear weapons? What if some uncooperative state were harboring terrorists who, we knew, were planning to strike?

I asked Kerry’s chief foreign policy adviser, Rand Beers, former head of counterterrorism in the Bush White House, whether his candidate ruled out military preemption in all cases.

“We don’t believe preemption should be a doctrine,” Beers said, in pointed reference to Bush policy. “But it would definitely be a tactic if necessary – for example, against terrorism.”

If Kerry can persuade the American public that he would be ready to use force if necessary, the poll figures might start shifting. Watch how he handles that issue in Boston this week.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.