It can be something as small as positioning the candidate at just the right camera angle or as big as catching the opponent in a campaign-altering slip of the tongue.
Every day, the ground troops of Team Obama and Team Romney set out in pursuit of a common goal: winning the day. Moment by moment, hour by hour, they scramble, maneuver and hustle to gain an inch here, a foot there on the opposition.
Driving it all is the belief that by stringing together enough small, daily victories, they can help their candidate win the one day that truly matters — Nov. 6, Election Day.
If they lose the day on Monday, they will work harder to win it on Tuesday. If they lose on Tuesday, there's always Wednesday or Thursday. Until time runs out.
Each day opens with a mental push of the reset button.
When Obama underperformed in his first debate Wednesday night, his handlers worked all the harder the next morning — in briefings, conference calls, television appearances, attack ads and more — to frame Romney's debate narrative as dishonest. Republican rapid responders served up rejoinders in real time.
Winning the day becomes a state of mind that motivates but also has the potential to distract.
It's what fires up the volunteers, the interns, the media monitors, the cable TV guests, the road warriors, the press wranglers, the local party officials and all the others who make up the infrastructure of a presidential campaign and propel it through long, wearying months and even years.
"It helps you get up at 5 in the morning so that the doughnuts and coffee are ready when the volunteers come in at 6 or 7," says Paul Begala, a Democratic consultant who helped create the 24-hour war room for Bill Clinton's winning presidential campaign in 1992.
Campaign partisans scour every word from the opposition in search of openings to exploit. Most of that turns out to be wasted effort. But no one knows what one sentence could veer off-message and end up becoming a Moment that will reverberate in the political echo chamber.
"Any change in direction is something that we can grasp on to and then use to get into the news cycle and get into the narrative," says Republican National Committee spokesman Kirsten Kukowski, whose emails fly at all hours.
Both incidents have become threads in the ongoing campaign narrative.
Other moments just pass by, quickly forgotten in the daily blur of a campaign.
—Romney's road team scrambles to set up an impromptu meet-and-greet when his plane lands in Ohio at about the same time as an honor flight of aging veterans just back from visiting Washington memorials.
"I'm drunk!" one vet announces as he carefully makes his way down the ramp. "Better now," he says when he reaches the ground.
"Better now!" Romney repeats.
Everyone poses for the camera.
—Obama's handlers let a muscular Florida pizzamaker hoist the president off the ground in a big bear hug during a drop-by at the man's restaurant.
"Look at these guns!" Obama enthuses about the man's biceps.
Everyone poses for the camera.
In theory, all of this moment-by-moment activity is supposed to reinforce the candidates' broader message to American voters.
"We had a good week last week. There's no doubt about it. We have to have a good week this week and the week after. So I think we take it one day at a time," Republican Party Chairman Reince Priebus said Sunday on CNN's "State of the Union."
Romney spokeswoman Gail Gitcho said GOP responders stand poised to tweet, email and otherwise magnify any misstep by the other side.
"We find our openings, pick our spots and then we drive it," she said.
Obama's campaign team members declined to publicly discuss their day-to-day operations, but carry out similar operations.
For any positive motion that can come out of a win-the-day mindset, there's a risk that campaigns can get so caught up in day-to-day skirmishes that they lose sight of the big picture.
Romney senior strategist Stuart Stevens likes to preach the long view. He's been known to remind staffers that "the key is winning the election, not winning the day."
But Begala thinks that message may have gotten lost by the Republicans, saying the Romney campaign has been "all over the map" with talk of the debt clock, violence in Libya, currency manipulation in China, and more.
Without a clear vision, he says, "every day becomes an Etch a Sketch, it becomes a zigzag."
But somebody still has to get up early and get the doughnuts.