SENATOR CARL LEVIN of Michigan had a grim and unhappy look on his face. For years, he had led Democrats in an effort to slash funding for missile defense. He had planned to seek a cut of $68 million. But with North Korea poised to launch missiles and Iran's relentless drive to go nuclear, the situation had changed. So much so that Senator Jeff Sessions of Alabama proposed to boost spending on the missile defense program, now more than two decades old, by an extra $45 million. Even Levin voted yes as it passed 98-0 in late June.

There are two lessons here. One is that Democrats, having kept spending for missile defense at anemic levels during the Clinton years, and having sought to block deployment of an effective system under President Bush, are vulnerable on the issue. And this is an election year in which Republicans, embattled and minimally popular, need every issue they can find. The other lesson is that an election campaign, with the American people paying attention, is the perfect time to debate missile defense and generate national support for a system on land, at sea, and in space. At the least, Democrats would be put on the defensive.

There's no doubt about either the popularity of missile defense or the urgency in deploying a full-blown system to protect America. In a 2004 poll by Princeton Survey Research, 62 percent approved of President Bush's plan to build a missile defense system. A year earlier, in a Gallup Poll, 61 percent said they would be "upset" if money were not being spent on such a system. And in a survey last year sponsored by a pro-missile defense group, 79 percent voiced support for missile defense and 70 percent said it is an "important part" of homeland security.

The need for an antimissile shield was underscored this summer not only by North Korea's missile tests and Iran's race to build nuclear weapons, but by the potential emergence of a worldwide threat. North Korea is believed to have a small nuclear arsenal and is an exporter of weapons. Iran, the world's leading sponsor of terrorists, is developing long-range missiles as well as nukes. If it produces a nuclear weapon, other Middle Eastern nations are likely to follow. Pakistan, an Islamic country with a fragile pro-West government, plans to build more nuclear weapons. And the United States would have no defense in the unlikely event that China or Russia, onetime enemies, unleashed a missile attack.

Bush boldly cleared the way for deploying a missile defense system by withdrawing, in December 2001, from the Anti-Ballistic Missile Treaty with Russia. A year later, he ordered Defense Secretary Donald Rumsfeld "to proceed with fielding an initial set of missile defense capabilities" by 2004 or 2005. These, the president said, "will include ground-based interceptors, sea-based interceptors, additional Patriot (PAC-3) units, and sensors based on land, at sea, and in space."

In 2004, a handful of antimissile missiles were deployed in Alaska. And six Navy ships have been equipped to bring down missiles. The head of the missile defense program at the Pentagon, Lieutenant General Henry Obering, insists these systems would have been able to destroy the one long-range missile fired by the North Koreans on July 4. That missile failed and fell in to the Sea of Japan.

But Obering is only guessing. And the widely held view in the defense community is that the deployment of anti-missile assets by the United States is not keeping pace with the growing missile threat. The war in Iraq, for one thing, has forced serious cuts in funding for missile defense. Planned deployments were delayed and the number of actual antimissile units was reduced. This year, House Republicans have sought to cut spending further.

There's a compelling case for re-engaging missile defense as a top priority of the Bush administration. A comprehensive upgrading of the ship-based Aegis system, which has been successful in eight out of nine tests, makes enormous sense, as ships can be deployed off the Korean coast and near Iran. Expanding the number of antimissile ships would be the fastest way to get near-global coverage at the least cost. Destroyers could probably be equipped for $100 million or less.