If you just squinted your eyes a little, and looked at only the first row of supporters at a campaign rally for President Obama, it might not seem all that different from four years ago. That raw electricity still radiates around him. At his rallies, supporters still sink their fingers into his back, middle-aged men still, on rare occasion, tear up in his presence, and crowds still stand out in the rain to hear him speak. But in general, they are smaller and less diverse. And if you look beyond the front row, there are more faces, not frozen in ecstasy, like before, but suspended in quiet, sometimes penetrating scrutiny. In 2012, Mr. Obama looks a little leaner and his hair is a little grayer. In New Hampshire, in a sweltering high school gymnasium, he closed his eyes, lost for a fraction of a second in solitary respite, as he used a handkerchief to dab the sweat off his forehead in the middle of his stump speech.

The Front Row 2012

The 2008 campaign offered voters a once-in-a-lifetime chance to make history, to be part of the nation’s grand collective memory. This year that offer is not on the table. This time around, Mr. Obama wears the dual uniforms of candidate and sitting president, and with them, the weight of the institution and four difficult years of service. He is no longer the abstract embodiment of intertwined notions of Hope and Change. He is the president, with a record to defend. He can no longer ask for a leap of faith, only for four more years. He can only push, as his campaign posters simply state, forward. Unlike the soaring language of the last campaign, utilitarian calls to “just vote,” squabbles over saving Big Bird and cures for “Romnesia.” are more likely to be heard by voters. It is a decidedly more down-to-earth affair. Only four years separate the two campaigns, but aside from the man at the middle of them both, covering the campaign this year feels so different.

A Historic Moment 2008

In photographs from 2008, the Obama campaign was a visible work in progress, constantly evolving through a long, bitter, winter primary season. The settings were as diverse as the crowds that inhabited them. At a rally in Carrolton, Tex., Mr. Obama roamed freely on the stage, unshackled to the teleprompter, microphone in hand, lighted from one side by the warm glow of tungsten filaments set against a cool fluorescent green ceiling. His stroll around the stage brought him within inches of my lens. In Miami, storm clouds gathered in the steamy evening sky as he gestured in silent silhouette. In the October homestretch, his events had the scale of sold-out rock concerts. You could feel this swell of energy and emotion as Election Day drew near.

Experiencing 2008

Photographers catch only a fleeting glimpse of the president beneath layers of armored stage decorations, lecterns, microphones, teleprompters, staff members and Secret Service agents. In photographs, Mr. Obama can often seem engulfed by the scale of the office and the necessary trappings of the presidency. Night after night, we watch him descend the ramp from Air Force One, salute his greeters, take a right turn and walk away to Marine One, the helicopter that carries him into the night sky and back to his home at 1600 Pennsylvania Avenue. A lone Marine tips his hat and bows into the rotor wash from the departing helicopters. It is mesmerizing, standing under the wing of Air Force One, watching the routine unfold, even though it is exactly the same every time. Campaigning can sometimes seem like a lonely undertaking for a man who is almost always surrounded by people. At the Iowa State Fair, Mr. Obama made a stop for a beer and pork chops and found himself alone with a plate of food in front of a crowd of reporters, photographers and fairgoers, but without a set of utensils so he could actually eat his food. He got little sympathy from his busy observers. Backstage at an event in Cleveland, after shaking dozens of hands he stood alone in front of the campaign’s instant presidential backdrop waiting for instructions on his next obligation and a dose of hand sanitizer.

The President on the Trail 2012

This time around many of his rallies have a small-town scale but lack the grassroots feel of ’08. They have a uniform, packaged gloss, typical of most presidential events. At a rally at a baseball field in Virginia the president came out swinging, literally, with an imaginary bat. But the crowd was squeezed into a corner of the stadium to give the illusion of density. Four years ago, he would have been speaking in the center of that stadium with supporters lining the field and filling the stands. In 2008, I observed him interacting with people more, not just as a solitary figure, standing at a microphone or shuttling from place to place. There is now a constant challenge to find candid, story-telling images. Every day on the trail is scheduled and scripted down to the minute, and covering it often feels like a carefully choreographed dance. In between rallies, there are a few “off the record” stops to local businesses and restaurants or official presidential duties, but most days are filled with this intricate series of repeating movements. Sometimes it feels as if we are just going through the motions, and I often wonder if he doesn’t feel the same way. At a stop in Colorado City, Mr. Obama sat on the edge of a wrestling mat and put his shoes on after meeting with some Olympic hopefuls. It was such a brief and rare humanizing moment, a reminder that the president of the United States of America still sits on the ground when he has to and still puts his shoes on, one foot at a time, just like the rest of us. We were quickly ushered away. At an event in Miami, speaking in front of an oversize American flag, he eventually draped his arm over the lectern, shifted the weight of his body and for a fleeting moment allowed his weariness to seep onto the podium and in through my lens.

An Incumbent's Campaign 2012