James Taylor was a dark-complexioned young man with thick black hair. Joe Biden was more dapper than usual, with a neat little moustache. Barack Obama looked decades too young, and a little too starry-eyed, as “Hail to the Chief” played and he held up his right hand to take the oath of office.

For a select group of U.S. government employees and members of the military, it was the role-play of a lifetime: On Sunday morning, on a stage in front of the Capitol, they stood in for some of the most powerful figures in the world — part of an elaborate dress rehearsal for the 57th presidential inauguration scheduled for Jan. 21.

As Capitol Hill residents jogged or walked their dogs in the early morning mist, the “president,” “first lady,” “vice president” and “second lady” stood on the Capitol’s east steps, watching the presidential escort, including the United States Army Band, the Old Guard Fife and Drum Corps, and honor guard members from each branch of the military.

The soldiers were real, though their weapons were ceremonial. U.S. forces don’t tend to use bayonets or espontoons in battle anymore. (“I wish,” said one of the young men carrying a rifle with a blade on the end.)

“It’s very exciting,” said Gregory Rock, corps sergeant major for the United States Army Old Guard Fife and Drum Corps, who will be attending his seventh inauguration. “A lot of the young service members, this is the closest they’re going to get to the president.”

Organizers began arriving at 3 a.m. to oversee the dress rehearsal, which was sparsely attended as compared with next week, when there will be approximately 10,000 people in the parade, including 5,500 members of the military, and a Mall filled with spectators.

Despite the logistical difficulties of screening so many people for the parade, “our biggest challenge, our enemy, is the weather,” said Air Force Brig. Gen. James P. Scanlan, who is responsible for the event’s day-to-day operations. In 1985, when the low temperature on Inauguration Day was 4 degrees below zero and wind chill temperatures dropped to between 10 and 20 degrees below zero, the oath of office was moved inside to the Capitol Rotunda and the parade was canceled.

Organizers this year have been closely watching the forecast for Jan. 21, which is currently predicted to be 42 degrees and sunny, Scanlan said.

In a sense, Inauguration Day will itself be kind of a stand-in for the real thing. Constitutionally, the president must be sworn in by noon on Jan 20; because that day falls on a Sunday, President Obama will take the oath of office in a private ceremony that day.

After the rehearsal parade marched down Pennsylvania Avenue to the White House, the political stand-ins returned to the stage on the Capitol’s west side for the “swearing in.”

The stage overlooking the Mall was filled with government employees in casual dress, wearing signs indicating whom they were playing: Senators, pop stars or other dignitaries.

They didn’t look like them. Often, they weren’t even the same gender.

“We’ve changed since we got out of office,” quipped a dark-haired young woman wearing a sign that read, “Former Senate Majority Leader and Mrs. Tom Daschle.” She said she was not authorized to give her real name or position.

A young woman next to her, whose sign read, “Former Senate Majority Leader Bill Frist and Guest,” added: “We all get along now.” That sent a young woman playing Mr. and Mrs. Newt Gingrich nearby into giggles.

“Beyonce!” someone yelled as a woman walked by who did not look like Beyonce.

Two 11-year-olds from suburban Maryland — Marie Clare Paxton and Quincy McElhaney — played first daughters Sasha and Malia. They were volunteered by Marie’s father, a Senate employee.

Perhaps the best physical match was Delandra Rollins, 20, a stately Army specialist from Dinwiddie, Va.,whose hair, stature and sparkly silver shoes evoked Michelle Obama.

After standing all day in the silver shoes, however, Rollins had some advice for the first lady’s feet. “Something not as high,” Rollins said. “Casual, classy, but also gorgeous.”

Serpico D. Elliott, the Air Force staff sergeant standing in for the president, said he had been selected purely for the way he looks. “I fit his physical build,” said Elliott, 29, who is 6 foot 2 inches and normally works on computer networks for the military.

Standing high up over the Mall, looking out over the expansive park that is expected to fill up with people on Inauguration Day, Elliott, who is from Greensboro, N.C., said he felt something he had never felt before.

“It was definitely a once-in-a-lifetime event,” he said, adding that it was thrilling to be looking down over the crowd rather than up from one. “It’s an amazing feeling — even if for a day.”