Once described by White House chief of staff Andrew Card as "one of the favorite people in the White House," Miers has been there for President Bush at every turn for more than a decade.
She was Mr. Bush's personal lawyer in Texas, took on the thankless job of cleaning up the Texas Lottery when he was governor, and followed him to Washington to serve as staff secretary, the person who controls every piece of paper that crosses the president's desk.
In 2004, Mr. Bush appointed her White House counsel, calling her "a talented lawyer whose great integrity, legal scholarship and grace have long marked her as one of America's finest lawyers." He articulated his high regard for her more memorably during a 1996 awards ceremony when he called her "a pit bull in size 6 shoes."
Though Miers has never served as a judge, Mr. Bush made the point Monday that she wouldn't be the first to reach the high court from a career outside the judiciary, reports CBS News White House Correspondent Mark Knoller.
"Justice Rehnquist himself came to the Supreme Court without prior experience on the bench, as did more than 35 other men including Byron White," he said.
However Democrats are sure to pounce on the fact that her views on key issues are largely unknown.
"Democrats and even some Republicans complained that there wasn't enough of a 'paper trail' when John G. Roberts, Jr., came to the Senate and was confirmed ... that no one really knew what kind of a person he was when it came to the law," said CBSNews.com Legal Analyst Andrew Cohen. "Well, there is even less of a paper trail for Harriet Miers."
Miers had been leading the White House effort to help choose a Supreme Court nominee, reports CBS News Correspondent Susan Roberts, but apparently the president decided he need to look no further than his own staff.
Miers, 60, has a string of firsts on her resume that track her quiet but steady march to the top echelons of power: first woman hired by her law firm in 1972, first woman president of the Dallas Bar Association in 1985, first woman president of the Texas State Bar in 1992, first woman president of her law firm in 1996.
Card, in a 2003 interview with the publication Texas Lawyer, said Mr. Bush's affinity for Miers is clear in the frequent invitations she receives to visit the presidential retreat at Camp David, "a privilege that is not enjoyed by a lot of staff."
"She's a quiet, highly respected force and someone who is seen as not having any agenda other than the president's," he said.