SEMPER FIDELIS?: Mark Callanan at the Democratic National Convention. IMAGE: Nigel Jaquiss

DENVER—As Arizona Sen. John McCain prepares to accept the Republican presidential nomination in Minnesota this week, it’s hard to escape the conclusion that the one-time “maverick” has lost his way in attempts—such as his puzzling choice of Alaska Gov. Sarah Palin as a running mate—to seduce his party’s conservative base.

The evidence is not just in Minneapolis-St. Paul. It was in Denver, too, at the Democratic National Convention last week.

Shortly before Sen. Dick Durbin (D-Ill.) introduced Sen. Barack Obama last Thursday, I left the press box at Invesco Field in search of somebody who had a real connection to the race. I circled around behind the speakers’ podium and made the dizzying climb to section 539, near the open end of the horseshoe-shaped stadium. There might have been a worse seat in the house. But not by much.

Sitting in seat 25 of section 539 was Mark Callanan, 21, of Rochester, N.Y., a brawny young man wearing a red Marine Corps T-shirt. He’s a senior at Geneseo State College in upstate New York, majoring in political science. He’s also a lance corporal in the Marine Reserves.

An infantry rifleman who volunteered for the Marines on his 18th birthday, he ships out to Iraq’s Anbar province on Dec. 1 as part of Alpha Company, the anti-terrorism Battalion of the 4th Marine Division. “They always send the infantry where the bad stuff is happening,” Callanan says.

Callanan was not the most likely person to have scaled Invesco’s heights. He is not a Democrat, nor is he pro-choice, except in cases of rape or other extremes.

And although Callanan was too young to vote in 2000, he supported John McCain’s unsuccessful presidential bid.

“I was a huge John McCain fan in 2000, but he’s changed,” Callanan said as he worked his way through a bag of peanuts. “No one can question his integrity, but he’s had to sell out to get the nomination this time.”

Callanan cites several examples of where he thinks McCain abandoned his principles, such as backing president Bush’s tax cuts after having voted against them and speaking at Rev. Jerry Falwell’s Liberty University after having previously condemned Falwell.

Still, despite his disappointment at what he saw as McCain’s pandering, Callanan says his respect for the former prisoner of war’s military record remained strong, making the decision on whom to vote for this November difficult.

Two weeks ago, Callanan traveled across the country to volunteer at the Denver convention. His older brother, who works in the Pentagon, wangled him a job working as a floor manager at the Pepsi Center.

“It’s a good résumé builder,” Callanan says.

The work was challenging. “I saw the worst in human nature,” Callanan says. “I almost got in a fight with an 80-year-old state senator from West Virginia on Tuesday. The Secret Service shut the floor down and the guy would not take ‘no’ for an answer.”

After three days at the Pepsi Center, Callanan’s reward was supposed to be a good seat at Invesco Field for Obama’s acceptance speech.

But when he arrived at the stadium early Thursday, he says he learned that many of the volunteers there had deserted their posts to claim seats. Pressed into duty, he spent the day helping to secure Invesco’s entrances.

By the time he was released from his duties, Callanan says, all he could find was a seat far above and to the rear of the podium.

Shortly after 8 p.m., he rose with the crowd as Obama took the stage to a mighty roar.

Callanan listened intently, particularly when Obama touched on military issues.

“The men and women who serve in our battlefields may be Democrats and Republicans and Independents, but they have fought together and some died together under the same proud flag. They have not served a Red America or a Blue America—they have served the United States of America,” Obama said.

Callanan cheered that message and the young Marine said he knew for certain Obama was his candidate.

Was it worth taking a week out of his life only months before he goes off to war to work until his feet bleed and to climb so high in the stadium that his nose almost did the same?

“Absolutely,” Callanan said, after Obama concluded his speech. “The man is going to be the next president.”