Lewis Libby, Vice President Dick Cheney's top aide, has been a quiet yet powerful force in shaping the Bush administration's policies and helped build the case for the Iraq invasion.
However, he has now been forced to resign his position after he was indicted Friday on five charges in the CIA leak investigation.
Libby has a scholar's demeanor and is known among colleagues for his analytical approach honed during years of work as an attorney.
Toiling long hours in his office in the building next to the West Wing of the White House, Libby steeped himself in subjects like counterterrorism, bioweapons defense and energy.
But the vice president's chief of staff also has a literary side -- he published a mystery novel, "The Apprentice," in 1996.
Set in rural Japan in 1903, the book was praised by Publishers Weekly for achieving "a sense of mystery and claustrophobia through pared-down prose and minimalist characterization."
Libby, 55, goes by his nickname, "Scooter," but many people also refer to him as "Dick Cheney's Dick Cheney."
"He is to the vice president what the vice president is to the president," said Mary Matalin, who worked with Libby as an adviser to Cheney during Bush's first term.
Speaking before the indictments, she described Libby as a deep thinker and problem-solver who gives "discreet advice."
Libby shares the vice president's hawkish views on national security and his penchant for operating behind the scenes.
"He doesn't grandstand," said World Bank President Paul Wolfowitz, Libby's friend and mentor.
Wolfowitz, former deputy defense secretary, said a major issue that Libby has focused on the past four years is the threat of a biological or chemical attack on the United States, a risk Cheney has often warned about in speeches.
Libby is known for a reluctance to being quoted in the press, but his private conversations with reporters caught the interest of prosecutor Patrick Fitzgerald, lead investigator of the leak of covert CIA operative Valerie Plame's identity.
Plame's diplomat husband, Joseph Wilson, accused the Bush administration of outing his wife to discredit him for accusing the administration of twisting intelligence to justify the Iraq war in a New York Times opinion piece on July 6, 2003.
Times reporter Judith Miller, who recently testified in the leak investigation, spent 85 days in jail for refusing to reveal her source, who turned out to be Libby.
In the Iraq war's run-up, according to journalist Bob Woodward's book "Plan of Attack," Libby presented a document to top officials citing evidence of weapons of mass destruction and possible contacts between Iraqi officials and a ringleader of the Sept. 11, 2001, attacks.
The weapons were never found and the administration has since backed away from the idea of a connection between Saddam's government and the Sept. 11 attacks.
Nickname for Yankee shortstop
Libby was given his nickname Scooter as a child after the Yankees baseball player Phil "Scooter" Rizzuto.
Born in Connecticut, Libby attended Phillips Academy, an elite private school in Massachusetts. He graduated magna cum laude from Yale University in 1972 and got a law degree from Columbia University three years later.
At Yale, Libby took a political-science course with Wolfowitz, who tapped him in 1981 to serve in the State Department in Reagan administration. Libby later served in the Pentagon under former President George Bush.
Wilson has said he believes Libby may have been part of a White House campaign to "smear" him.
Wolfowitz said Libby has never been "a rabidly partisan political type."
"There is a difference between people who focus on policy and people who believe it's my party right or wrong -- that's not Scooter," he said.
Before he worked for Cheney, Libby was a managing partner at the international law firm Dechert, Price and Rhoads.
Among Libby's more controversial clients was Marc Rich, the wealthy financier and fugitive who was pardoned by President Clinton in 2001.
In addition to his interest in creative writing, Libby, who is married and has two children, is also an avid skier.
A September letter sent to Miller in jail, which played a role in her decision to testify, showed Libby's literary side.
"You went to jail in summer. It is fall now. You will have stories to cover ...," he wrote. "Out West, where you vacation, the aspens will be turning. They turn in clusters, because their roots connect them. Come back to work -- and life."