As I watched Secretary of State Hillary Clinton’s Benghazi testimony Wednesday, one thing that struck me was the sight of a familiar figure over her shoulder. Those of us who covered the legal travails of both Clintons during the 1990s, and their rocky relationship with the investigation-inclined Republican Congress would have instantly recognized Cheryl Mills. She is a rare figure in Washington, one who put loyalty and discretion ahead of ambition.

And she is ferocious.

Mills is now the counselor and chief of staff to Clinton at the State Department. In the Clinton Administration, she served as deputy White House counsel, and was one of the most influential voices behind the scenes. The internal clashes usually centered on whether to turn over what the president’s enemies were demanding, or to hunker down and fight. She almost invariably led the resistance, an inclination that Hillary Clinton shared.

Few of us outside the inner circle of the White House actually got to hear that voice until Bill Clinton’s impeachment trial in the Senate. The BBC called her “the shining star of the defense team,” an assessment that just about everyone else in Washington shared.

“We cannot uphold the rule of law only when it is consistent with our beliefs,” Mills argued that day. “We must uphold it even when it protects behavior that we don’t like or is unattractive or is not admirable or that might even be hurtful.”

The BBC wrote: “She slapped down both the obstruction of justice charge and the House case that leaving Mr. Clinton in office would undermine the rule of law.”

David Von Drehle, then of the Washington Post, added:She followed Gregory B. Craig, a blooded veteran of that busy intersection where politics and litigation collide. And it was a bit like watching Liza Minnelli follow Judy Garland – both knew what they were doing, both had their fans, but only one was a virtuoso.” 

But when the top job — White House counsel – -came open in 1999, Mills turned it down. It would have been a chance to make history. At only 34 years old, she would have been the first woman and the first African-American to hold that position. But by then, she was burned out. It was time to move on.

”I can’t,” she told my late friend Robin Toner, a reporter for the New York Times. ”But it made me sad.” Mills returned to government, however, when Clinton became Secretary of State, again in a role that kept her behind the scenes. That she should be there beside Hillary in yet another trial on Capitol Hill must have felt familiar indeed.