Faced with an unending scandal about her use of a private e-mail server when she was secretary of state, Hillary Rodham Clinton decided last September to “reset” her presidential campaign. As Amy Chozick wrote in the New York Times, the new Hillary would display her “humor” and her “heart,” the qualities that her friends say rarely come across in public appearances.

The reset reached its zenith on October 3 when Hillary appeared on Saturday Night Live as “Val,” a bartender to whom Kate McKinnon, as Hillary Clinton, pours her heart out. The six-minute segment ends with “Hillary” and “Val” bonding as they sing “Stand by Me,” the Ben E. King classic. “Hillary” gets so carried away with her manic crooning that she doesn’t realize “Val” has disappeared and been replaced by cast member Cecily Strong, playing a character known as “Huma.” “I was just hanging out with my best friend Val,” Hillary says. Huma tells Hillary there is no one there. “I think you’ve had one too many, Hillary, let’s go,” Huma says.

Huma, as anyone who follows politics knows, is 40-year-old Huma Abedin, Hillary Clinton’s “shadow,” as Politico once described her. She began working for Hillary in 1996, when she was a 19-year-old intern fresh from George Washington University assigned to the First Lady’s office. Abedin had wanted to be a journalist like her hero Christiane Amanpour and was hoping to work in the White House press office. “Take a chance,” her mother told her. “Don’t fall in love with Plan A.” Huma took the advice. “Sixteen years later, I wouldn’t change a thing,” she told a dinner audience in 2012, at a Fortune conference. “And I got to meet Christiane Amanpour.”

Over the years Huma has served in several positions, with increasingly important-sounding titles. She has been Hillary’s “body woman,” her traveling chief of staff, a senior adviser, and a deputy chief of staff when Hillary was secretary of state. Now, based in Brooklyn, she is the vice-chair of Hillary’s 2016 presidential campaign. But whatever the title, the job she performs for Hillary has always been essentially the same: confessor, confidante, and constant companion. It’s safe to say that over the years Abedin and Hillary have spent more time together than either has with her husband.

A former adviser to Bill Clinton describes her as “a mini Hillary.” Wherever Hillary goes, Abedin goes. In November 2008, when Hillary flew to Chicago to meet with President-Elect Barack Obama to discuss becoming secretary of state, she took Huma along. During Hillary’s grueling, nearly 11-hour congressional testimony in October about Benghazi, Abedin was there. She has been referred to as a “second daughter” to the Clintons. Others have described Hillary and Huma as like sisters.

Whoever wants to curry favor with Hillary has to go through Abedin, as thousands of recently released e-mails make abundantly clear. For the quotidian matters of the schedule, she speaks for Hillary, and people adept at getting access to Hillary know it. “Everybody fights to be at the center,” the former adviser says, “and Huma controls a lot of that dynamic.”

“I’m not sure Hillary could walk out the door without Huma,” Clinton adviser Mandy Grunwald told *Vogue’*s Rebecca Johnson eight years ago. “She’s a little like Radar on *M*A*S*H. If the air-conditioning is too cold, Huma is there with the shawl. She’s always thinking three steps ahead of Hillary.” It’s still true today. Nothing Hillary-related is too big or too small for Abedin’s purview. Take, for example, the secretary of state’s December 2009 struggle to get a faxed document: