John McCain's schedule today calls for a flight from Washington to Wisconsin. A town hall meeting in Oshkosh, a second one in La Crosse and a dinner in Milwaukee. Then, the Republican presidential front-runner flies home to Arizona.
The fatigue of the campaign trail may be the one issue on which the four top presidential candidates agree.
Fellow Republican Mike Huckabee and Democrat Barack Obama also have events in Wisconsin, and Hillary Clinton will be on the stump in Ohio.
So goes the months-long, morning-to-night test of stamina known as the presidential race, an uber-marathon that requires candidates to maintain focus and energy amid the travel, stress and fatigue of a national campaign.
"I'm finding out just how long I can go sleep-deprived. Running for president is like being waterboarded," Republican candidate Mike Huckabee told CNN's Larry King. He was only half-kidding.
Fatigue is one issue on which the candidates agree.
"You try to sleep whenever possible, which is usually on planes or in the car. And some days, you know, there is not enough caffeine in the world to keep you going. You just have to plow through," Democratic candidate Hillary Clinton said.
Traveling across time zones and not having a daily routine can make it more difficult to get enough sleep, said Dr. Rick Kellerman of the American Academy of Family Physicians. Research has shown that fatigue can affect learning and memory.
Kellerman does not think stress is an issue for the candidates, despite the public appearances and media scrutiny.
"These are people who have learned to cope with stress. In fact, they may even thrive on stress," he said.
Schedule-packed mornings make it hard to get regular exercise and eat healthy foods.
Clinton likes spicy food and credits a chemical in hot peppers, capsaicin, with keeping her healthy since 1992. Research has shown that it can lower blood pressure and cholesterol, even fight some cancers.
Spicy food or not, the brutal schedule appeared to have caught up with the 60-year-old New York senator last week when she suffered several coughing spells. She has company. In the days before he dropped out of the race, several of Democrat John Edwards' speeches were interrupted frequently by his coughing.
The campaign produced a health scare in December, when then-Republican candidate Rudolph Giuliani turned his charter flight around and was rushed to a St. Louis, Missouri, emergency room with a severe headache. After leaving the hospital, Giuliani said that there was nothing more to it. A campaign aide said the 77 campaign events in 53 cities that month had simply caught up with him.
Life on the campaign trail illuminates some of the health concerns of the remaining four candidates.
Huckabee, 52, has appeared to be the most diligent about exercise, jogging four or five days a week. As governor of Arkansas, Huckabee weighed 280 pounds and was found to have type 2 diabetes. He said he now weighs 185 to 190 and is symptom-free, thanks to exercise and an improved diet. Dr. Sanjay Gupta reports on how the candidates stay fit. »
As a skin cancer survivor, McCain wears caps outside and avoids the sun on the campaign trail. McCain, treated in 2000 for invasive melanoma, said he has a clean bill of health and sees his dermatologist every three months.
At 71, McCain is the oldest of the candidates and would be the oldest person to be elected president. Ronald Reagan was 69 when he was elected.
Questioned about his age during a campaign stop, the Arizona senator pointed to his 95-year-old mother as evidence of good genes and added, "I work 24-7. I'm very active. I enjoy life. I am involved and engaged."
Everywhere he's gone, Obama has had Nicorette gum close at hand. The 46-year-old said he quit smoking before launching his presidential campaign at the insistence of his wife, Michelle.
Young or old, Kellerman said, there are no guarantees when it comes to health.
"There are things that happen to people that we cannot predict, that we cannot prognosticate. So we can develop a risk profile, but in the end, we can't tell exactly who's going to have what and when." E-mail to a friend
David S. Martin is a senior producer with CNN Medical News.