The reaction from the average American probably would be, "So what?" What difference does it make now?
But for Supreme Court watchers, her concession is at least a small temblor on the Richter scale.
For those who felt O'Connor was "in the tank" with the Bush campaign -- the Washington expression usually describes a journalist too closely tied to a politician -- her concession may be the ultimate irony.
Which is not true, of course.
The ultimate irony was that even if the hand recount ordered by the Florida Supreme Court been allowed to go on, the odds are good then-Texas Gov. George W. Bush still would have won the presidency. Florida provided the electoral votes to put Bush over the top in the election.
An audit by the accounting firm of BDO Seidman commissioned by The Miami Herald, USA Today and others, found that if the U.S. Supreme Court had let the Florida Supreme Court order stand, Bush would have widened his 537-vote lead over Vice President Al Gore to 1,665.
That's counting all paper ballots not completely punched through -- those infamous "hanging chads" -- but obviously showing a voter's intent.
The Herald looked at one scenario where Gore could have won, pbs.org reported.
The audit did not include recounts in seven counties that had been completed when the U.S. Supreme Court stepped in and stopped the process. A more lenient recount of those counties tolling the intent of the voters would have allowed Gore to eke out a close victory and claim the White House.
In an interview with the Chicago Tribune Editorial Board, O'Connor, now 83, questioned whether the case should have been heard by the U.S. Supreme Court at all.
O'Connor was named the high court's first woman justice by President Ronald Reagan in 1981.
The Supreme Court "took the case and decided it at a time when it was still a big election issue," O'Connor told the Tribune board. "Maybe the court should have said, 'We're not going to take it, goodbye.'"
She said the decision "stirred up the public" and in a classic understatement, said the outcome in Bush vs. Gore "gave the court a less-than-perfect reputation."
"Obviously the court did reach a decision and thought it had to reach a decision. It turned out the election authorities in Florida hadn't done a real good job there and kind of messed it up," O'Connor told the Tribune. "And probably the Supreme Court added to the problem at the end of the day."
The reaction from left-leaning media and blogs was pretty much "too little, too late." But was O'Connor "in the tank" with Republicans even before the controversial ruling in Bush vs. Gore?
True or not, O'Connor is reported to have been aghast when CBS News prematurely called Florida for Gore, telling guests at an election party in Arizona, "This is terrible."
Linda Hirshman, liberal author and Supreme Court historian, cited further evidence of her partisanship in an April 30 article for The New Republic.
While researching for a book about O'Connor and Justice Ruth Bader Ginsburg, Hirshman said, she came across a letter O'Connor wrote to Barry Goldwater, former Republican presidential candidate and a close friend, before the 1988 presidential election in which Republican Vice President George H.W. Bush claimed victory.
"A week until election day," O'Connor wrote to Goldwater. "Despite your advice, the campaign never really hit the basic issues. People are tired of it all. Many will not vote. I will be thankful if George B. wins. It is vital for the [Supreme] Court and the nation that he does."
But in an interview published last month in the Los Angeles Times, O'Connor praised President Obama's 2008 election and predicted: "One of these days we'll have a Hispanic president, I would imagine. It will be very important to those of our citizens who are Hispanic. If we get a woman president one of these days, I'll be excited."
She mentioned no candidates.
In 2000's Bush vs. Gore, the narrow majority said in a "per curiam," or unsigned, opinion -- actually written largely behind the scenes by O'Connor and Justice Anthony Kennedy -- that the recount authorized by the Florida Supreme Court violated the equal protection guarantees of the Constitution.
Holding that the "individual citizen has no federal constitutional right to vote for electors for the president of the United States" except under a form set by a state legislature, the majority said the Florida court's ruling did not say who would recount the votes. Letting local entities do the recount, and letting local judges ensure its fairness, would result in a number of recount methods in individual counties, the ruling said.
"Upon due consideration of the difficulties identified to this point," it said, "it is obvious that the recount cannot be conducted in compliance with the requirements of equal protection and due process without substantial additional work."
But that "additional work" had to be done by the "safe harbor" date set by the state Legislature, Dec. 12, so that the state's electoral votes could be cast in the Electoral College -- in other words, it had to be done in the two hours left on the day when the opinion was released at 10 p.m., and approved by the Republican Secretary of State Katherine Harris.
Justice John Paul Stevens, one of the four vehement dissenters, was clear in his scorn for the majority opinion.
"The Constitution assigns to the states the primary responsibility for determining the manner of selecting the presidential electors," Stevens wrote. "When questions arise about the meaning of state laws, including election laws, it is our settled practice to accept the opinions of the highest courts of the states as providing the final answers. On rare occasions, however, either federal statutes or the federal Constitution may require federal judicial intervention in state elections. This is not such an occasion."
Stevens said the "federal questions that ultimately emerged in this case are not substantial."
"Admittedly, the use of differing sub-standards for determining voter intent in different counties employing similar voting systems may raise serious concerns," he said. "Those concerns are alleviated -- if not eliminated -- by the fact that a single impartial magistrate [local circuit judges under the Florida Supreme Court order] will ultimately adjudicate all objections arising from the recount process."
Stevens said, "Even assuming that aspects of the remedial scheme [the recount allowed by the Florida Supreme Court] might ultimately be found to violate the equal protection clause, I could not subscribe to the majority's disposition of the case. As the majority explicitly holds, once a state legislature determines to select electors through a popular vote, the right to have one's vote counted is of constitutional stature. As the majority further acknowledges, Florida law holds that all ballots that reveal the intent of the voter constitute valid votes. Recognizing these principles, the [U.S. Supreme Court] majority nonetheless orders the termination of the contest proceeding before all such votes have been tabulated. Under their own reasoning, the appropriate course of action would be to remand send down to the lower court] to allow more specific procedures for implementing the Legislature's uniform general standard to be established."
Stevens, now 93 and enjoying a comfortable retirement in Florida, at the time reserved his most powerful language for his final statement.
"What must underlie [the Bush campaign] petitioners' entire federal assault on the Florida election procedures," he said, "is an unstated lack of confidence in the impartiality and capacity of the state judges who would make the critical decisions if the vote count were to proceed. Otherwise, their position is wholly without merit. The endorsement of that position by the majority of this [U.S. Supreme] Court can only lend credence to the most cynical appraisal of the work of judges throughout the land.
"It is confidence in the men and women who administer the judicial system that is the true backbone of the rule of law. Time will one day heal the wound to that confidence that will be inflicted by today's decision. One thing, however, is certain.
"Although we may never know with complete certainty the identity of the winner of this year's presidential election, the identity of the loser is perfectly clear. It is the nation's confidence in the judge as an impartial guardian of the rule of law."