When David Muir has to helm the Good Morning America news desk — as he often does — he relies on two lifesavers: a Bose alarm clock with a very large snooze button and the alarm on his BlackBerry, both set to 4:30 A.M. "I check the time three times before I can fall asleep," the ABC reporter and anchor admits. But in late January, another electronic sentry rousted him two hours before that as his cell phone chimed with news that John Edwards, whom he'd been trailing during the presidential primary campaign for almost a year, was ending the chase.

It's a few weeks later, and as Muir ducks out of his ABC office — coatless in a snowstorm — to grab lunch, he recaps that busy day: the 6:00 A.M. flight to New Orleans, back-to-back one-on-ones with the candidate and his wife in front of some FEMA trailers in the Lower Ninth Ward, a live World News report, and, finally, the last possible flight back to New York. By the time he could bunk down on the Upper West Side again, it was exactly 24 hours since that first wake-up call — giving him just two more hours before the pinging and blaring would get him up again for the morning show.

Muir, 34, is not alone when it comes to sleep deprivation during this campaign season. The most competitive primary race in a generation has disturbed the circadian rhythms of many a striver in the media and political professions alike. Muir's job hurtles him from state to state in search of perspectives from both regular people and the powerful, and his passport is always handy. "You never know," he shrugs, flashing a business card scrawled with a half-dozen frequent-flier numbers and tucking it back into his wallet.

On a campaign swing through South Carolina, Muir revealed a few rituals that keep him going — a daily multivitamin, a tepid Starbucks he'll nurse for hours, gallon after gallon of bottled water — but about the only thing that's routine in this line of work is the arrival of the unforeseen. Muir's job, through all of the distractions, is to distill the news for the broadest possible audience. "If you're asking questions that are relatable to the people who are watching," he says, "the candidates and their spouses will generally answer those, even if they're not always easy. They respect you for that." While many of his ABC colleagues were assigned to a particular candidate long ago, the long road to the general election ensures that Muir, who drops in on all the contenders, traverses a huge swath of the nation and its political — and personal — landscape. (A recent live interview with Barack Obama found Muir asking the candidate, essentially, if he and Oprah Winfrey spoke on some sort of special Batphone.)

Now, though, Muir's been sent to the other side of the state — along with his laptop, a fearless producer, and a rental car equipped with GPS — in search of Hillary Clinton. In a shrinking news industry, on-air talent are increasingly called on to do everything — shoot footage, write a blog, anchor a webcast — and Muir has embraced multitasking with the enthusiasm of NBC's Brian Williams, to whom he is often compared, and the élan of the late Peter Jennings, whose encouraging words he still carries with him. Like both men, Muir got his start young, as a teen gofer for a local station in Syracuse. While still attending Ithaca College, he both anchored and produced a weekend newscast there, timing segments at the anchor desk with a yellow stopwatch even as he was delivering them — and then driving 60 miles to meet his buddies for Saturday night's last call.