"She will be an outstanding addition to the Supreme Court of the United States," Bush said during a press conference announcing his pick.
Saying she has a "record of achievement with the law," Bush said Miers also has "built a reputation of character and integrity" and possesses a "deep compassion and abiding sense of duty."
"She will bring that same passion for service to the Supreme Court of the United States," he added.
If confirmed, Miers, 60, would join Justice Ruth Bader Ginsburg (search) as the second woman presently serving on the nation's highest court.
"I am very grateful for the confidence in me that you've shown by this nomination and certainly I am humbled by it," Miers told Bush during the press conference.
The White House is describing the nominee as "a woman of many firsts," including being one of the first staff members to arrive at the White House each morning and among the last to leave. She is known for thoroughness and her low-profile.
When Bush named her White House counsel in November 2004, the president described Miers as a lawyer with keen judgment and discerning intellect — "a trusted adviser on whom I have long relied for straightforward advice."
He added: "When it comes to a cross-examination, she can filet better than Mrs. Paul."
In making his announcement on Monday, Bush stressed that his nominee will not legislate from the bench. Conservative Republicans in recent years have complained that too many judges have been "activist" in their rulings in not strictly interpreting the Constitution on issues such as gay marriage and end-of-life issues.
"It is the responsibility of every generation to be true to the founders' vision of the proper role of the courts in our society," Miers said. "If confirmed, I recognize that I will have a tremendous responsibility to keep our judicial system strong and to help ensure that the courts meet their obligations to strictly apply the laws and the Constitution."
Supporters call Miers a great lawyer who understands the limited role they think judges should play in society and the importance of strictly adhering to the Constitution.
"In nominating Ms. Miers, the president has reaffirmed his commitment to appointing judges who will respect the rule of law and not legislate from the bench," said Noel Francisco, former assistant White House counsel and deputy assistant attorney general during the Bush administration.
Miers headed for the Capitol to begin courtesy calls on the senators who will vote on her nomination within hours of being nominated.
Senate Republicans said they would press for confirmation by Thanksgiving.
"It is an enormous appointment, replacing Justice O'Connor, and we will be very, very thorough. To the extent we can meet a timetable we will but thoroughness will be our goal," Senate Judiciary Committee Arlen Specter, R-Pa., said after a meeting with Miers.
Later in a press conference, Specter added: "Everything I know about Ms. Miers is good but I do not know a great deal about her professional activities or her academic standing or her work in her legal career, which appears to be a very distinguished career. ... There needs to be, obviously, a very thorough inquiry into her background as a lawyer and her activities."
Appeasing Both Side of the Aisle
A lawyer who has never been a judge, Miers was the first woman to serve as president of the Texas State Bar and Dallas Bar Association. She also was the first woman to become president of a large law firm in Texas — Locke, Purnell, Rain & Harrell — with a staff of 200 attorneys.
White House officials and some political observers said Miers is conservative enough to satisfy the president's supporters and does not have a lengthy legal record that could give Democrats much ammunition against her.
But others say Bush perhaps took the easy way out by picking Miers rather than someone like Priscilla Owen (search), who undoubtedly would be more controversial but more pleasing to conservatives.
"It looks an awful lot like he flinched," said Bill Kristol, a FOX News contributor and publisher of The Weekly Standard. "He put up someone with no judicial record and it's hard to interpret that as anything but flinching from a fight."
Republican strategists said they would have to work hard to assure the support of some of the more conservative Republicans in the Senate. All 55 GOP senators voted to confirm Roberts.
But not all conservatives are shrugging at the nomination.
"I think she is a wonderful choice. She has gone through some of the same experiences Sandra Day O'Connor" did and is considered one of the top lawyers in Texas, Sen. Kay Bailey Hutchison, R-Texas, told FOX News.
"I think it's very important to have someone on the bench who has been a practicing lawyer ... you need that real-world experience that brings another dimension to the Supreme Court."
Senate Democrats for months have been warning Bush to pick what they call a "consensus nominee" whose ideology lies somewhere in America's "mainstream." They also continuously called on the president to include them in nomination discussions to make sure the person who was chosen for the court appealed to both sides of the aisle.
White House spokesman Scott McClellan said the president consulted with more than 80 senators on the nominee to replace O'Connor. Miers had initiated several of those contacts between White House and the Senate.
"They recognized that she is someone who had the kind of qualifications and experience and judgment that was needed to serve on the nation's highest court," McClellan said, adding that Bush and Miers met several times about the potential nominee before Bush made the decision on Sunday night to nominate his longtime friend and colleague.
White House Chief of Staff Andy Card called newly-installed Chief Justice John Roberts (search) early on Monday morning before Miers was notified by the president of his final decision around 7:15 a.m.
"She has earned the respect and admiration of the legal profession and she will earn the respect and admiration of the American people," McClellan added.
Democrats are under pressure from liberal interest groups to fight Bush's second Supreme Court pick, and many observers speculated prior to the nomination that the fight for O'Connor's seat would be even more brutal than that Roberts, who started his new job on Monday. Confirmed last week on a 78-22 vote, Democrats were evenly split on confirming Roberts.
Some observers had said even though some Democrats wanted to vote "no" on Roberts, they voted "yes" so that their "no" vote on the next nominee was more acceptable.
"All I can say to those who thought there was some tactic in that — they're dead wrong, they don't know me. They don't understand my Vermont groups. They don’t understand a senator who votes his conscience," Sen. Patrick Leahy, the ranking Democrat on the Judiciary Committee who voted for Roberts, said Monday. "I wrestled with that decisions … I made up my mind because I thought John Roberts was qualified to be chief justice."
He said with regards to Miers that he'll participate in the hearings and spend time with the nominee "with an open mind."
"Is this somebody who can come in and look at each case as it is or will she feel that she is, has to be bound to the philosophy of the president who appointed her?" Leahy asked.
Some Republicans have said they believe Democrats may even attempt to filibuster (search) Bush's pick for the court because Roberts got afairly easy pass, even if the current nominee isn't necessarily that far out of the mainstream.
"My view on that is, the Constitution does not allow for a supermajority to be appointed to the Supreme Court," Sen. Charles Grassley, R-Iowa, told FOX News Monday morning. "Never has a filibuster stopped somebody from being on the Supreme Court."
Bush said the "American people expect Harriet's hearing to be handled with the same respect and civility that characterized the last three Supreme Court nominations" of Roberts, Ginsburg and Stephen Breyer.
Sen. John Cornyn, the Texas Republican who served as a type of point-person in the Senate for the administration while Roberts was being shepherded through the confirmation process, said Bush's pick is a great choice.
"It is important that we put aside partisanship, and that the Senate fulfill its constitutional responsibility of advice and consent," he said. "This fine nominee must be treated with civility and respect, not as a political pawn. I hope that we in the Senate can move forward in a manner worthy of the American people."
Senate Democratic Leader Harry Reid issued a statement saying he likes Miers and adding "the Supreme Court would benefit from the addition of a justice who has real experience as a practicing lawyer." Reid had personally recommended that Bush consider Miers for nomination, according to several sources familiar with the president's consultations with senators.
Lack of a Paper Trail
Bush noted Monday that neither the late Chief Justice William Rehnquist (search) nor 35 other Supreme Court nominees had judicial experience before being named to the country's highest court. He also reminded the country that both Republicans and Democrats have encouraged a nominee that doesn't necessarily have a judicial background.
Reid said he looked forward to the "process which will help the American people learn more about Harriet Miers, and help the Senate determine whether she deserves a lifetime seat on the Supreme Court."
House Democratic Leader Nancy Pelosi of California said because O'Connor has played "a pivotal role in preserving our civil liberties and Americans' right to privacy, including a woman's right to choose, Ms. Miers must face scrutiny on her positions on these matters.
"The Senate should seek full answers from Ms. Miers regarding respect for the Constitution, including limits on the Executive branch's power, the independence of the judiciary, civil rights, and the right to privacy. Ms. Miers has the burden of demonstrating that she shares Justice O'Connor's commitment to our freedoms, and is suitable for a lifetime appointment to the Supreme Court," Pelosi added.
Sen. Charles Schumer, D-N.Y., was up in arms when Roberts would not give details on his opinions on certain hot-button issues or cases that likely would come before the court during his confirmation hearings.
"There is some hope that Harriet Miers is a mainstream nominee, a very preliminary view indicates very little that she wouldn't be," Schumer said during a press conference Monday. "This is a good first day in the process that begins to fill the seat of Sandra Day O'Connor."
Schumer said Bush has recognized that "the views of the extremist wing of his party are not the views of the American people."
"We are certainly, we Democrats, are going to look at this nominee with a complete and open mind," he added. "Having said that, we know less of this nominee than we did about John Roberts in terms of" judicial philosophy and temperament.
With no record, observers say the White House and Miers should be prepared for a firing squad of questions during her Senate confirmation.
Asked if Democrats will be tougher on Miers than they were on Roberts, FOX News Supreme Court analyst Tim O'Brien said, "I don't know if toughness is the word.
"This is such a critical appointment. She is going to be subjected to the most exacting scrutiny and I think that's appropriate … they are going to challenge her understanding of constitutional law."
Grassley said Miers has "kind of a blank slate" as far as judicial history is concerned.
Sen. Dianne Feinstein, a Democrat from California who voted against Roberts after saying she simply did not know enough about his views to be comfortable voting to confirm him, said Monday that while she's had some "good conversations" with Miers, the lack of judicial record will require careful scrutiny.
"My view is, always wait for the hearings" and do due diligence before forming an opinion, Feinstein said. "I'm delighted by the fact that she is a woman … Sandra Day O'Connor leaves behind big shoes … this is a very pivotal nominee."
O'Connor was considered a swing voter on the court for years who has cast deciding votes on some affirmative action, abortion and death penalty cases.
Democrats also already are calling for the White House to release writings and papers of Miers'. The White House authorized the release of almost 80,000 documents from Roberts' tenure in the solicitor general's office during the Reagan administration but said those written during the George H.W. Bush administration were protected under attorney-client privilege.
"Given how little we know about this nominee other than her work as the president's lawyer, the White House needs to disclose all documents requested by the Judiciary Committee, and Ms. Miers needs to explain her thoughts on constitutional interpretation," said Sen. John Kerry, D-Mass.
Formerly Bush's personal lawyer in Texas, Miers came with the president to the White House as his staff secretary, the person in charge of all the paperwork that crosses the Oval Office desk. Miers was promoted to deputy chief of staff in June 2003.
She grew up in Dallas, earning her undergraduate and law degrees from Southern Methodist University. She also served as a member-at-large on the Dallas City Council. In 1992, she became the first women president of the Texas State Bar. She was the first woman of the Dallas Bar Association in 1985.
The Associated Press contributed to this report.