Washington ? Sometimes the best antidote against political propaganda, or spin, is to hold on to your notes. That is what I did during and immediately after the Democratic convention last week in Boston.

A typical comment from the John Kerry campaign came from spokesman Jeremy Van Ess at 8:51 a.m. Friday, just as Kerry and John Edwards were setting out on their current cross-country campaign trip. “Kerry and Edwards will campaign from sea to shining sea, riding a surge of momentum out of the Boston convention,” he proclaimed in an e-mail. A little more than two hours later, Van Ess said “Kerry and Edwards are riding a wave of momentum following the convention, with America still buzzing about Kerry’s acceptance speech.”

This week, polls showed Kerry and the convention apparently had failed to move the dial on this election very far. The Washington Post-ABC News poll showed Kerry leading President Bush by 2 points among those most likely to vote. “By historical standards,” said Washington Post polling director Richard Morin, “Kerry’s post-convention bounce is modest, at best.”

And Tad Devine, Kerry’s media adviser, declared, “We never expected great movement in the polls.” Of course not. That’s why they scripted every moment of the four-night convention, including most especially Kerry’s own speech.

As one of the distinct minority of journalists who was not blown away by Kerry’s performance, I was not surprised at the apparent lack of progress by the Democratic challenger. I thought it was pretty clear that Kerry had not bombed but also that he had not hit a home run — and I said exactly that on PBS’ “Washington Week” on Friday evening and in a column written in the predawn hours on Friday for Sunday papers around the country.

What strikes me now is that many of my colleagues — and perhaps the Kerry campaign itself — are missing the significance of Kerry’s lost opportunity.

The importance has relatively little to do with the polling numbers. Those will change. What is vital is that this was the first test — and in some ways the easiest — for the truly unconventional campaign message strategy Kerry and his advisers have adopted.

Normally, the challenger to an incumbent president has two main tasks to perform during convention week. The first is to present a fuller picture of himself, one that is more comfortable to the voter. The other is to lay down in strong terms the case why the man in office should be replaced.

Kerry and other speakers fixated on one brief shining moment in his pre-political career: His valiant service as a Navy officer in Vietnam. It became the all- purpose metaphor — “I’m John Kerry, and I’m reporting for duty.” But it never really merged with the story of his later life, and the American people are plenty smart enough to remember that throughout the 1990s, Democrats insisted that Bill Clinton’s avoidance of military service during Vietnam was no disqualification for his serving as commander in chief.

Left largely unanswered — or only vaguely outlined — was the question of what Kerry had done with his life in the decades since he came home from Vietnam, particularly in his 20 years of Senate service. President Bush immediately pounced on the omission, suggesting in his very first speech since Kerry’s nomination that the senator has few “results” for which he can claim credit as a legislator. The charge is unfair, but Kerry left himself wide open to it.

As for indicting the incumbent administration, Kerry and other speakers soft-pedaled their criticism — or couched it in cliched terms. And they left unanswered what may be the single biggest question on the minds of undecided voters: What exactly would Kerry do differently to bring the bloodshed in Iraq to an end and secure a stable democracy there? The answer, apparently, is to ask allies for more help, but that calls for a leap of faith. It is not a political strategy.

Iraq was the almost unmentionable subject in Boston, and voters may well have felt cheated.

What the Democrats did do was to challenge Bush directly on two of his assets — his reputation as a strong leader and a man with strong values. Kerry said — and others affirmed — that he too is strong of character and strong of will. It is unusual, to say the least, to build a challenger’s campaign on the incumbent’s main strengths, but that is what the Kerry team has done.

It does not appear to have worked this past week, and now the news focus shifts to the Olympics, the Republican convention and the continuing threat of terrorism. It will be weeks before Kerry has another such opportunity.