A Supreme Court nomination, as President George Bush has made clear, can be a president's greatest and most lasting legacy. It took bruising battles, but Bush brought real change to the court, which he turned to the right with his successful nominations of John Roberts and Samuel Alito.
As president, Barack Obama can undo many of Bush's programs and policies. But he won't be in a position to change the Supreme Court until a justice or two decides it's time to go -- and even then, it depends on which justice retires and who is tapped (and confirmed) as the replacement.
It seems likely Obama will get a shot at creating a legacy of his own. At least one justice is expected to retire over the next four years, and possibly up to three. Five justices, after all, are 70 or older. John Paul Stevens is 88.
That means that as much as Bush pointed the court in a more conservative direction -- on abortion rights restrictions, on racial preferences, on religious liberty -- the next president could achieve even more dramatic change. With the court closely divided by one vote on those and other controversial issues, the next president could have a profound impact on its direction with a single nomination.
On that point, both sides agree. Outside advocacy groups on the right and left are pouring time and money into the issue, seeking to rally supporters and attract independent voters by highlighting how dramatically the next president could shape the court -- and American life -- for a generation.
"There is no single issue on which the next president, by himself, will have any greater impact than the Supreme Court," said Wendy Long, counsel to the conservative Judicial Confirmation Network, which has been running television advertisements in key battleground states.
"The future of the Supreme Court and probably the law as we know it over the next 40 years are at stake," Kathryn Kolbert, president of the liberal group People for the American Way, said at a recent forum.
The court now is split between four solid judicial conservatives (Roberts, Alito and Justices Antonin Scalia and Clarence Thomas) and four liberals (Stevens and Justices David Souter, Ruth Bader Ginsburg and Stephen Breyer). Moderate conservative Anthony Kennedy is the new "swing vote." He usually sides with conservatives, but on some issues, such as the death penalty and the scope of presidential power, he votes with the liberals.
With that kind of lineup, one new justice could shift the balance of power. But most court watchers believe McCain, not Obama, could have made the most pronounced shift in the court, at least in the short-term.
That's because the three most likely contenders for retirement are all liberal: Stevens, who will be 92 at the end of the next administration; Ruth Bader Ginsburg, who is 75; and David Souter, who has reportedly told friends he'd like to return home to his native New Hampshire.
Replacing them with a conservative would minimize Kennedy's role as the swing vote and turn the court further to the right on key issues like race, the environment, religion, abortion, the death penalty and the war on terror.
Take, for example, the court's recent rulings on executive power in the war on terror. It has repeatedly rejected Bush's policies for detaining terror suspects at Guantanamo Bay, Cuba, ruling most recently in June that suspects have a right to challenge their detention in federal court. That landmark decision was 5-4, with Kennedy joining the four liberals to cast the key vote.
Or abortion. Right now, the court is at least one vote short of overturning Roe v. Wade. Only Scalia and Thomas have said they would overturn it; Roberts and Alito have not yet ruled on the issue. But Kennedy, who has supported abortion restrictions, has nonetheless refused to overturn Roe and helped send the issue back to the states to decide. One new justice could make a difference.
Obama, on the other hand, voted against Roberts and Alito. He has said he would nominate justices who believed the court should take a more active role in protecting people's rights, and he often uses the case of Lilly Ledbetter, an Alabama woman who lost a pay discrimination claim on a five-four vote, to make his point.
But Obama would probably just be holding a liberal place card. If he replaces Stevens, Ginsburg or Souter, it won't change the balance of the court.
Here, though, history can be a cautionary guide. In 2005, court watchers expected Chief Justice William Rehnquist to give Bush his first Supreme Court vacancy. While Bush would have an historic opportunity to nominate the next chief justice, he wouldn't be changing the court's direction -- he would just be replacing a conservative with a conservative.
But moderate conservative Justice Sandra Day O'Connor delivered a bombshell: She announced her retirement first, giving Bush the opportunity to change the court, which he did when he replaced O'Connor with the more solidly conservative Alito.
If a conservative justice delivered a similar bombshell in the Obama administration, President Obama will then have an historic opportunity of his own to turn the court's direction. With Democrats controlling the Senate, Obama could quickly undo Bush's legacy.
By replacing a conservative justice, Obama would turn the court to the left with his nomination. That would make the court more liberal than it's been in decades -- and more receptive to affirmative action, discrimination claims, drawing firm lines between church and state and numerous other social issues where conservatives have held sway.