What a body man does depends on the politician. Senator John Kerry’s aide for his presidential race in 2004 was dubbed “part butler, part buddy.” Bill Clinton’s aide when he was president said their relationship sometimes felt more like that of an old married couple. Senator Hillary Rodham Clinton has a body woman, the efficient and glamorous Huma Abedin. On NBC’s “The West Wing,” President Josiah Bartlet treated his body man, Charlie Young, like a son.

Mr. Obama said he regarded “my guy, Reggie,” as the kid brother he never had. “But maybe I’m saying that just because he technically could be my son,” the Illinois senator said. “I don’t want to admit my age.”

Image Reggie Love is Senator Barack Obamas right-hand man. Credit... Doug Mills/The New York Times

Mr. Love said he had been hired with “no job description whatsoever.”

“It was just like, ‘You just go out there and  Take. Care. Of. Stuff,’ ” Mr. Love said, taking his time with each word.

Some of the “stuff” Mr. Love takes care of: When Mr. Obama makes calls to woo superdelegates, Mr. Love is at his side with a briefing book, dialing the numbers. When an outdoor speech ended on a windy day in Noblesville, Ind., he appeared behind Mr. Obama as he shook hands on the rope line. “Jacket?” he asked, a coat draped at the ready over his arm.

When Mr. Obama dropped food on his tie while eating in the car between stops, Mr. Love was ready with a Tide pen. He always carries one, along with ballpoint pens, and has turned himself into a walking dispensary of Sharpies, stationery, protein bars, throat lozenges, water, tea, Advil, Tylenol, Purell and emergency Nicorette, not to mention his ever-present iPhone, BlackBerry and Canon Rebel XT digital camera. (Mr. Love keeps a photo journal of the campaign, and has more than 10,000 pictures so far.)

Compared with the even-tempered and self-controlled Mr. Obama, Mr. Love is raffish, always joking with the Secret Service, offering closed-fist high-fives to members of the news media and making frequent appearances in the daily pool reports. At a V.F.W. hall in Indiana, he helped out when the senator did not want a second Budweiser, taking it off Mr. Obama’s hands.