President Bill Clinton, right, practices his speech for the upcoming State of the Union address with members of his staff at the White House. Minyon Moore, then-deputy assistant to the president and deputy director of political affairs, is pictured second from left. (BARBARA KINNE/THE WHITE HOUSE)

Minyon Moore has been a key figure in national Democratic circles for more than 20 years, working for Jesse L. Jackson’s presidential campaign and Bill Clinton’s White House a decade later. She would likely be a key adviser to Hillary Rodham Clinton should the former secretary of state run for president in 2016.

Preferring to operate quietly and out of public view, Moore is also a regular contributor to District charities, particularly those helping inner-city youths. She is known as a mentor to countless young professionals eager to get involved in politics.

News of Moore’s alleged role in a secret get-out-the-vote effort for Clinton’s 2008 campaign has thrust her out from that behind-the-scenes spot where she has comfortably operated for decades. Now, according to court documents and interviews, she is a potentially key figure in an investigation into an allegedly far-reaching, off-the-books campaign.

“Minyon has been in this city for years operating aboveboard,” said political analyst Donna Brazile, who described Moore as one of her best friends. “When Minyon sees a wrong, she tries to make it right.”

The pro-Clinton spending, which was not reported, was revealed Wednesday in court documents and interviews. They are part of a broader, 18-month investigation into D.C. businessman Jeffrey E. Thompson and are not expected to lead to a separate criminal probe into Clinton’s unsuccessful 2008 campaign, people familiar with the case said.

In a statement this week, Dewey Square Group, the consulting firm where Moore works, said Moore has been “fully cooperating” with the federal investigation and “was entirely unaware of any inappropriate activities.”

The court documents show that Thompson secretly pumped more than $600,000 into a canvassing effort on behalf of Clinton in at least four states during her primary battle against Barack Obama, who was then a senator. The documents do not name Moore but describe a person affiliated with the campaign whom several people with knowledge of the case identified as Moore.

According to the documents, Moore helped connect Thompson to a New York marketing executive who headed the canvassing effort. That executive, Troy White, pleaded guilty Wednesday to mis­demeanor tax charges. White appears to have been one of those young operatives whom Moore liked to take under her wing, according to people who know Moore and are learning more about White this week.

Moore, 55, heads Dewey Square’s multicultural and state and local affairs practices.

Known as “Minnie,” she was described in interviews with friends as a master political strategist, an effective organizer and a philanthropist who prefers that her donations remain anonymous. Even in organizing events, like the recent 50th anniversary of the March on Washington, she likes to remain uncredited.

Moore, who lives in 16th Street Heights, is so shy that she was embarrassed last month at the funeral of New York political strategist William Lynch when singer Bebe Winans announced that Moore had requested a song. “She almost hid under the pew,” Brazile said.

Moore also quietly has helped youths at the Southeast Tennis and Learning Center, founded by former D.C. first lady Cora Masters Barry.

Barry said Moore was recently responsible for 10 young people from the center performing a “Blacks in Wax” performance, in which they portrayed civil rights icons at the White House during the week of the March on Washington anniversary. “She does it very quietly,” Barry said. “Nobody knows that. She wouldn’t even let us recognize her.”

In a March 2012 Q&A of the group with the Los Angeles Sentinel, Moore said her highest priority to her community was “to use whatever God-given talents I might have to inspire a new generation of leaders to make their mark on life in a positive and constructive manner.”

Benjamin Jealous, president of the NAACP, said he was part of that new generation and knew of Moore when he was 13 and volunteering on the Jackson campaign. As a 24-year-old Rhodes Scholar, he finally met her, and she nominated him to a White House fellowship. She took young people “from the hallways of power to positions of power,” Jealous said.

Brazile said she and Moore are members of a group of black female political operatives that they call “The Colored Girls” — all with their own distinct traits. Brazile is the TV pundit; Moore prefers to stay in the background and avoid interviews. Brazile likes to drink scotch and can be foul-mouthed; Moore is not known to drink and rarely curses.

Their common mission, Brazile said, is not about self-promotion but to help their communities. Brazile called them “political birth mothers.”

Consultant Regena Thomas, a former New Jersey secretary of state, was on the road from Atlantic City on Thursday morning to be by her best friend’s side. “She would never have done anything that was borderline being dishonest or illegal,” Thomas said.

Moore honed her skills in Chicago politics, joining a pipeline of African American political operatives into national politics through Jackson’s Rainbow PUSH Coalition and his presidential runs. Moore, the daughter of a post office employee and a factory worker, volunteered at PUSH while she was a student at the University of Illinois at Chicago. She worked at the post office and at Encyclopedia Britannica to pay for college, Dewey Square confirmed Thursday.

By 1992, she was assistant to Bill Clinton and director of White House political affairs, serving as a principal adviser to the president and first lady. In 2000, she was named chief operating officer of the Democratic National Committee.

Virginia gubernatorial candidate Terry McAuliffe was the DNC chairman at the time. In his 2008 book, “What a Party!,” McAuliffe wrote: “My first official act as chairman was to name Minyon Moore as my chief operating officer. Minyon was one of the classiest, most talented women in American politics, as well as one of the most loyal. . . . Minyon and I agreed that we were really going to shake up the party together.”

Moore has always had an interest in the arts and movies, said longtime friend Catherine “Kiki” McLean, a senior adviser on Hillary Clinton’s 2008 campaign. Moore also studied filmmaking, and business records show that she has been involved with a Los Angeles entertainment firm. According to a Hollywood Reporter story in April 2013, NBA Hall of Famer Isiah Thomas came up with an idea for a talk show after talking to Moore, his friend.

Locally, Moore has appeared to stay out of city politics and government. But her alleged role in the Thompson case has thrust her into a sweeping corruption investigation that centers on the 2010 mayoral campaign of Vincent C. Gray.

The revelations are the first to connect Thompson, believed to have secretly funded a $650,000-plus operation to help Gray win, to a national political figure.

Tom Hamburger and Jennifer Jenkins contributed to this report.