North Liberty (United States) (AFP) - With a smooth stride and relaxed posture, Beto O'Rourke was literally running for US president on Saturday. 

He began his campaign in Iowa by running a five-kilometer (three-mile) race in a respectable time at the start of a much longer contest for the Democratic presidential nomination.

The race in the Iowa City suburb of North Liberty allowed O'Rourke, an athletic-looking 46 years old, to project an image of youthful vigor -- in unspoken contrast to some of his much older political rivals. 

O'Rourke announced on Thursday that he would seek the nation's highest office, and his presence in Iowa was no accident: It is one of the earliest, and thus most important, states to hold presidential nominating contests. 

As the rising Democratic star set off on the local footrace Saturday -- one surely less treacherous than the much longer competition toward the Democratic nomination -- AFP and a gaggle of other reporters, supporters and simply curious Iowans tried to keep up.

O'Rourke's run last year for a United States Senate seat from the very-Republican state of Texas fell just short, but as he criss-crossed that vast, convervative state -- visiting every one of its 254 counties -- his energy and evident star power made him an object of media fascination.

"Is that the guy running for president?" one runner shouted as the Iowa race was about to start.

Dressed in black running gear, the six-foot-four (1.9-meter) Texan appeared relaxed, happy to shake hands or pose with fellow runners before turning serious, hand on heart, for the singing of the national anthem.

O'Rourke's is a long-time runner whose father Pat, who died in a 2001 bicycling accident, was an accomplished athlete.

He moved up slowly through the pack as the race unfolded, running side-by-side at first with a local engineer, Chuck Soat.

"He ran a lot faster than what he told me he would," Soat, 59, said afterward. He had kept up with the younger man long enough to hold a far-ranging conversation before finally falling behind.

They talked about global warming, tariffs and more, Soat said, struggling to catch his breath after the race. "I wish I could have kept up with him... He's a very approachable, very humble guy -- and a good runner."

'He has the stamina'

After leaving Soat behind, O'Rourke -- having doffed his vintage wool cap from the 1988 Calgary Olympics -- found himself in conversation with Noah Syme, 32, a doctor originally from New Mexico who shared his passion for music with O'Rourke, once a member of a punk rock band. 

As they ran under a bright sun that quickly made runners forget the overnight chill, the conversation soon turned to the US healthcare system. 

"I'm new to the State of Iowa and I'm trying to learn what's important for people here, and I think he's trying to do the same thing," Syme said at the finish line. "We talked about the race and healthcare, which is something I think he cares specifically about.

"Based on this race, he seems like he has the stamina to run for president. Very approachable, very nice guy."

Having crossed the finish line in well under 25 minutes, and then shouting encouragement to other arriving runners, O'Rourke, his forehead still glistening, took time to talk to a small crowd about the longer race -- the one for the Democratic nomination.

'Where I find my energy'

"We've got to run a campaign, and this is the toughest way to run," he said. "We are setting the pace... It is extraordinarily energizing."

"Getting back to the hotel at 10 or 11 (at night), I come down from all the energy that I have, all the stories I have heard, the people I have met, all the places I have been to for the first time. It's thrilling."

"That's where I find my energy."

Under the eye of countless cameras, the candidate/runner -- a rower during his student days at New York's Columbia University -- then walked over to his rental car, slipped into the driver's seat and headed out.

In an unusually crowded Democratic field of well over a dozen, opinion polls show O'Rourke among the top handful of candidates, his youthful charisma clearly a selling point for many voters. 

A prominent likely rival, 77-year-old Senator Bernie Sanders, slipped in his shower Friday, gashing his forehead and requiring seven stitches.