This week's Senate debate on Elena Kagan is less about confirming President Barack Obama's second Supreme Court nominee than about the future.
For the Republicans and their conservative allies, it's an effort to set limits for her tenure and what looms as a far more contentious confirmation battle over Obama's next selection, assuming he has one.
For Obama and the Democrats, it's about installing a justice to counter the court's increasingly conservative drift, recognizing that may be harder to do the next time.
Conservative groups have questioned Kagan's role as solicitor general in shaping the administration's health care reform legislation to meet legal challenges to its constitutionality.
They argue she should not participate in the proceedings if those challenges reach the Supreme Court.
That won't likely happen, since the justices themselves decide whether such a conflict exists, and Kagan has minimized her role in administration deliberations.
Republican senators, meanwhile, have criticized Kagan's lack of a judicial record and signs of her openly liberal views, such as opposing military recruiters at Harvard because she disapproved of the Pentagon's "don't ask, don't tell" policy.
Because she hasn't been a judge, they can't dissect decisions as they did during last year's proceedings on Obama's first nominee, Sonia Sotomayor.
As has become the norm, the GOP has argued that almost everything a judicial candidate has done or written is relevant, whether on the bench, in other positions or even in school.
That signals their likely approach if Obama nominates a political figure, such as Homeland Security Secretary Janet Napolitano or Massachusetts Gov. Deval Patrick, instead of a judge.
The GOP argument that Kagan would be an "activist" justice is somewhat ironic in view of the current court's conservative activism. But both parties share blame for these increasingly ideological nomination battles.
They began in the 1960s when conservative senators of both parties blocked President Lyndon Johnson's ill-timed effort to elevate the late Abe Fortas to chief justice and have escalated since.
Top Democrats, including Obama and future Vice President Joe Biden, exacerbated the trend by opposing the clearly qualified John Roberts on ideological grounds during the last Bush administration.
While half the Senate's Democrats backed Roberts, their opposition to later Bush nominee Samuel Alito was as monolithic as the GOP opposition to Kagan.
That partisan divide means Obama may have to pick a noncontroversial judge or a popular political figure to win confirmation in a Senate that, after November, will have a smaller Democratic majority or a Republican one. GOP moderates could hold the balance.
While Obama won't pick someone likely to vote consistently with court conservatives, he'll have to pick someone more acceptable to the GOP than Sotomayor or Kagan.
He also may feel compelled to correct the court's demographic, educational and geographic imbalance.
It now has six Catholics, three Jews and no Protestants; four graduates apiece from Harvard and Yale law schools (Ruth Bader Ginsburg started at Harvard and graduated from Columbia); and eight (all but Anthony Kennedy) who have spent most of their careers in the East.
That argues for choosing a Protestant, probably a white male, with a non-Ivy League background, who would be acceptable to enough Republicans to prevent a GOP filibuster and ensure confirmation.
Obama interviewed two Protestant appeals judges for the current vacancy: Diane Wood, a University of Texas Law School graduate, and Sidney Thomas, a graduate of the University of Montana Law School; plus Merrick Garland, an appeals judge considered less liberal than Kagan (though Jewish and a Harvard Law School graduate).
Wood and Thomas may prove too liberal to fit future circumstances. But their inclusion suggests awareness of the need for demographic diversity.
One unanswerable question is whether a Republican Senate would use filibuster rules to block a future Obama nominee. Some Republicans floated that threat this time.
It might depend on whether that nominee replaced Ginsburg, a liberal who is 78 and has been ailing, or one of the five more conservative justices.
The latter would produce a fight that could make this debate look like a walk in the park.
Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News. Readers may write to him via e-mail at firstname.lastname@example.org.