You might think that a cause that has the support of 82 percent of the American people would have a fairly good chance of prevailing on Capitol Hill. But you would be wrong. A clownish senator and a distracted president have managed to bring the Comprehensive Test Ban Treaty to the brink of meltdown. It's not that it would be voted down on the Senate floor. It's just that Sen. Jesse Helms won't let it get there.

This is not the first time that the chairman of the Senate Foreign Relations Committee, who comes from North Carolina and basically hates the rest of the world, has denied his colleagues the right to vote. In 1997, he stood in the Senate door to block consideration of another matter of grave consequence to the country and the planet, the Chemical Weapons Convention. Helms, who glories in being impossible, set his face against it. Republican Senate leader Trent Lott backed him. Sen. Richard Lugar of Indiana, who is regarded by the right as unacceptably rational, rallied like-minded Republicans on the committee to challenge Helms. Lott and Helms finally gave way.

But Lugar is playing no part in the current drama. He wasn't asked. He has not heard from President Clinton, nor has he received battalions of briefers like those of other years who must explain the technical complexities of verification.

Lugar is not the only member of the Senate who feels the president is not concentrating on an issue that is rich in legacy potential and has the Kennedy connection Clinton is usually so eager to seize. John F. Kennedy's finest hour was the Limited Nuclear Test Ban Treaty. Democratic senators led by Minority Leader Tom Daschle and Joe Biden, the ranking Democrat on Foreign Relations, think they forced the president to speak out on the treaty last week in the Rose Garden. Seven of them held a press conference organized by the Coalition to Reduce Nuclear Dangers. Two Republican senators, James Jeffords of Vermont and Arlen Specter of Pennsylvania, joined in a demand for the release of the treaty.

Biden denounced as "stupid and ridiculous" Helms's insistence that the president seek Senate approval of two other treaties before the test ban could be considered. Helms opposes both the ABM agreement with Russia, which has expired, and the Kyoto Accord, which calls for reductions in greenhouse gasses. Biden says neither of them has anything to do with the test ban.

Lugar's absence from the ranks of moderate Republicans supporting the test ban is keenly felt. So is that of John Chafee of Rhode Island, a stalwart on arms control at home and abroad--he wants a ban on handguns. But he is otherwise engaged, trying to save the ABM Treaty from extinction.

"The CTBT is not anyone's top priority," mourned a GOP staffer.

Some muse that the president, a compulsive compartmentalizer, feels he has expended his quarterly foreign policy component by his attention to Kosovo and has returned happily to his first loves, budget and taxes. His National Security Council expert, Bob Bell, says senators will not concentrate on the issue until a time certain for consideration is set. But Republican senators would like to be sure the treaty is a winner before they declare themselves. The more they hang back, the more the chances of success are diminished. Only the president can reverse the tide.

"We have not given up," says Bell, but his imminent departure--he is off to NATO for an arms control post--has increased Capitol Hill calls for a point person, preferably some grandee either Republican or military or both, a big name like Adm. William Crowe or Gen. Colin Powell, who could knock heads together and give professional reassurances about verification and other knotty matters.

"We have not given up," says Bell.

Lugar says they have: "The administration is giving up--the degree of energy needed is simply not there."

Majority Leader Lott has made it clear he will not intervene this time. "We took it away from the chairman on chemical weapons and there were a lot of problems," he says. This is South-speak for "hell to pay" after the liberation and passage of the CWC. "I am not inclined to do that again."

Some say that the nuclear explosions in Pakistan and India illustrate the futility of the ban now, although proponents say it would inhibit deadly progress. Some think the treaty is untimely because the North Koreans are madly making missiles.

If Clinton wants it, he will have to mobilize the favorable 82 percent. They may not grasp Senate dictators, egos, etiquette or nervous Nellyism. But they know that a nuclear test ban does not deserve incineration by inaction, the fate it now faces.