Politics is a battle of inches. An expression here, a sound bite there can often mean the difference between celebration and commiseration.

A litany of reasons has been given for Rudolph W. Giuliani's political collapse in this presidential race: He bypassed all the early primary states, showed an almost obsessive focus on 9/11, had dodgy associates and embraced a social policy agenda out of step with mainstream Republicans. True enough, but they ignore a more significant Giuliani campaign failure: the inability or utter unwillingness to communicate a presidential vision of America and the country's future.

I worked as Mr. Giuliani's pollster from 1993 through 2001. I watched in awe as he turned New York City around, proving that you could, in fact, govern an "ungovernable" city. He personifies exactly what Republicans want most in a leader. He was a man of explicit words, relentless action and an unmatchable record of results on crime, welfare, job creation and tax reduction.

Yet just a month after the first caucus vote, Super Tuesday is here, and Rudy Giuliani is gone. What went wrong? How could the best-known candidate in the field spend $40 million and earn just a solitary delegate?

In this case, the conventional wisdom is wrong. Mr. Giuliani did not collapse under the weight of a failed strategy. And it wasn't his stand on the issues. It's that this incredible communicator had no theme. No focus. No discipline. And no campaign team with the heart and guts to fight to keep the campaign message on track within a chaotic political environment.

I have conducted extensive focus groups for Fox News over the last eight months. I have sat down with more than 1,000 voters in Iowa, New Hampshire, South Carolina, Florida and Nevada as they watched the seemingly endless series of presidential debates.

Every focus group yielded a clear winner and a clear loser. More often than not, my phone would ring in the post-debate hours with calls from debate winners and losers, wanting to know what worked, what did not, and why. Mr. Giuliani was the only top-tier Republican candidate never to "win" one of these sessions, and his campaign aides never called to ask why until it was too late.

I wish they had. First, I would have told them that time constraints do matter. These presidential debates are, in essence, 60-second pitched battles. When answering a question that requires genuine knowledge and substance, candidates still need to grab the audience with an opening sound bite, hold their attention with brief policy details and then close with an applause line. Brevity, clarity and simplicity are simply the hallmarks of good communication.

This unforgiving trial-and-error process rewarded candidates such as Mike Huckabee and Sen. Barack Obama, because they learned to adapt to the rules. Mr. Giuliani, in contrast, was the candidate most likely to be cut off by the moderator. Nothing antagonizes my focus group participants more. Worse, he was the least likely to be interrupted by applause.

Ideologically, Mr. Giuliani's greatest stumble wasn't on abortion or gay marriage. It was immigration. His exchange with Mitt Romney in the Tampa, Fla., debate was an unmitigated disaster. He accused Mr. Romney of taking a holier-than-thou position on the issue, to which Mr. Romney responded: "I'm sorry, immigration is not holier than thou, mayor. It's the law." The man who had brought order to lawless New York was hoisted by his own petard.

Here is a man who turned New York City around by standing his ground on principle. As his final term drew to a close, he was proved right, his critics wrong. But presidential candidate Mr. Giuliani got mired in linguistic small potatoes. He would recite micro-level statistics from his term as mayor but fail to connect the dots for the audience on a macro level. Participants in my focus groups were baffled by his long-winded, underpowered debate responses.

His ads, which few people saw because he was spending so much on private jets and stays at five-star hotels, were equally mystifying. Rather than real people - or Rudy himself - talking about how New York had changed, his campaign used unseen voice-overs to tell his story, which destroyed the message of credibility in the eyes of the viewer.

Mr. Giuliani did not lose this campaign; the campaign lost this campaign. His advisers should have been screaming in his ear, but instead they sat idle - frightened and intimidated by the prodigious potential president they were hired to help elect. At one point, I heard Mr. Giuliani suggest that his own polling showed he was winning the hearts and minds of the electorate.

A more candid assessment by his team six months ago would have yielded a more successful candidacy today.

Frank Luntz, a Republican pollster, is the author of "Words That Work: It's Not What You Say, It's What People Hear." This article originally appeared in the Los Angeles Times.