Over a period of more than 30 years I covered presidential campaigns and the White House. Regardless of how well planned and well-intentioned the people who undertake to lead the nation are, their success or failure is often determined by photo ops.

On election eve in 1968 I witnessed a remarkable sight. Presidential Republican candidate Richard Nixon had just touched down at an airbase in Orange County, Calif. The sun had set in the western sky, and as Nixon emerged from the United charter to come home to vote, the sound of massed bands filled the air, playing "Ruffles and Flourishes." From a stadium at the edge of the tarmac, hundreds of cheerleaders formed an aisle to the bottom of the ramp at planeside. They all held flaming torches, leading to the entrance to the stadium that had been built for the event. Nixon walked down the corridor to a stage, where none other than John Wayne was waiting to greet him for his last rally of the campaign.

DOUBLE TROUBLE: This photograph of President Clinton clenching his jaw while sitting next to a furious first lady Hillary Clinton was the cover of TIME as the Monica Lewinsky scandel erupted. Photograph by Dirck Halstead from MOMENTS IN TIME

This spectacle was the brainchild of a senior Nixon advance man, Tim Elbourne. Several weeks earlier I had entertained him at my apartment in New York during a campaign stop. I had a 16mm print of Leni Riefenstahl's famous documentary, "Triumph of the Will," which had been filmed during a Nazi party rally in Nuremberg in 1934 that consolidated Adolph Hitler's rise to power. As I turned off the projector, I saw a weird light appear in Elbourne's eyes. Landing in Orange County, he told me, "You're about to get a big surprise!"

Elbourne was the master of the "photo op." Each day he would scan the front pages of newspapers to see how they were playing pictures of Nixon on the campaign. Although Nixon's campaign manager, Herb Klein, prided himself on how many minutes the candidate got on the evening newscasts, Elbourne, on the other hand, would define success simply by looking at the front page of The New Daily News.

It was John Kennedy who really created the idea of the "photo op," as a way of crafting his image. He surrounded himself with photojournalists such as George Tames of The New York Times, Stan Tretick of Look magazine and Paul Shutzer of Life, making sure they had exclusive access to him during the campaign. Jacqueline Kennedy was no shrinking violet when it came to shaping her image with photographs, by anointing photographer Jacques Lowe to document her role as first lady.

What Kennedy's and Nixon's handlers realized was that a still image had a lasting impact when it came to public perception, far more than television. Further, by crafting events that would show off their candidate or president in the best light, a powerful message could be delivered, free of the commentary of reporters.

For some reason, the Republicans seem to grasp this idea more than Democrats. Ronald Reagan was a photographer's dream. Being an actor by trade, he in many ways regarded the Oval Office as his "set." The photo op actually became the reality. Not only was the public's perception of the "Gipper" defined by these photographs, but his policies were also shaped the same way. Even the Soviets began to understand how formidable these images became, as he stood in front of the Berlin Wall and called out, "Mr. Gorbachev, TEAR DOWN THIS WALL!"

Jimmy Carter, on the other hand, never got it. Formless cardigan sweaters and baggy raincoats would shape his image. In fact, two photographs stand out as representative of the perception of Carter. One was when, against the advice of his advisors, he decided to run in a marathon near Camp David, and nearly collapsed halfway through the event. The next day, newspapers around the world displayed the picture of the exhausted president on their front pages, under the headline, "American Mission to Rescue Hostages in Iran Ends in Desert Disaster." On another occasion, while vacationing in Georgia, a rabbit started to swim in circles around Carter's boat while he was fishing, and the president started to flail away at it with his oar. This photograph became known as the "attack of the killer rabbit."

Michael Dukakis may have been on his way to a victory in the presidential campaign of 1988 when a hapless advance team decided to let him take a ride in a tank at the General Motors plant in Michigan. Arthur Grace, a photographer for Time magazine, seeing what was about to happen, turned to the campaign manager and said, "It's all over!"

Gerald Ford also became a victim of the lens. Ford was one of the best athletes who ever occupied the Oval Office, but one slip on a slick stair coming off of Air Force One in Europe became a defining moment that he endured throughout his presidency, as comedian Chevy Chase endlessly did pratfalls playing the president in countless "Saturday Night Live" sketches on NBC.

PLANE SILLY: George Bush makes a Halloween announcement to the press on his campaign plane in 1978. Photograph by Dirck Halstead from MOMENTS IN TIME

George H.W. Bush loved to be around photographers. He called them his "Photo Dogs."

He was very at ease in front of the cameras. Unfortunately, his sense of humor often projected itself as simply being "goofy." Whether it was grimacing as he swung his golf club or holding a doll of his wife Barbara during a campaign appearance, the images drove his handlers crazy. Actually, one photograph may have been his final undoing during the '92 campaign. While visiting a grocers' convention in New Orleans, he was photographed standing near a cash register as a new system of inventorying by computer was being unveiled. One reporter in the pool remarked, "Look at him. He's never been in a checkout line!" That line, along with the picture, defined a president who many thought was "out of touch" with ordinary Americans.

Bill Clinton liked to model himself after John Kennedy. Actually, photographers used to call Kennedy "Jack The Back." That was because the president had a habit of turning his back to photographers until he was fully in control of how he wanted to look. Clinton, like Kennedy, was a master of projecting his image. His face just seemed so full of empathy. He could tear up at the drop of a hat when the occasion demanded it. For six years, I felt I could never get past that mask. Finally, as the Monica Lewinsky incident became public, Clinton was sitting next to the first lady at an event in Maryland. The news the night before had been full of the latest revelations. The first lady on this occasion was having nothing to do with him. Feeling the acute chill, Clinton's jaw muscle started to clench. This went on for minutes. Finally, I thought, "I've got you!"

My friend, John Morris, who is active in the American Democratic Party in Paris, blames me singlehandedly for the Democrats' defeat in 2000. He insists that my photograph of Clinton embracing Monica Lewinsky at a fund-raiser in Washington just before the 1996 election was the "smoking gun" that eventually led to his impeachment proceedings.

The photograph had sat unnoticed in boxes of images that I had taken during the 1996 campaign, until the first photographs of Monica Lewinsky began to surface following the election. Even though I had never seen the photograph, I remembered that face. Somewhere, I thought, I had photographed her with the president. Weeks later, a researcher working for me, going through thousands of photographs stashed in a light room at Time in Washington, found that single image.

The rest, as they say, is history.

Regardless of how we get our information, whether it's in print or on the World Wide Web, it is still the power of photography to isolate those moments in time.