There is no precedent or principle that should prevent a duly elected president from making a nomination to the Supreme Court, or the Senate from considering it, with nearly a year left in their terms. But Senate Majority Leader Mitch McConnell (R., Ky.) and others have understandable motives for attempting to invent one. Rejecting or ignoring a qualified nominee would be much more difficult and potentially embarrassing to the Senate than claiming that some time-honored maxim won't allow it to fulfill its constitutional obligation until next year.
Justice Antonin Scalia's death Saturday deprived the court of a giant among modern conservative legal thinkers as well as a narrow right-leaning majority that had expanded the right to bear arms, dismantled campaign-finance restrictions, and put George W. Bush in the White House. Under the circumstances, President Obama can serve the country and the court best - while making mere obstructionism a less viable strategy - by nominating a centrist without pronounced partisan or ideological loyalties.
He and the Senate can look to the example of another longtime - albeit sometime - member of the conservative majority, Anthony M. Kennedy. Confirmed at about this point in the last year of Ronald Reagan's presidency, Kennedy also happens to be the high court's least ideologically predictable member, having written last year's landmark ruling recognizing a right to same-sex marriage in the face of withering dissent from Scalia.
For all his uncompromising and often vitriolic advocacy, Scalia himself evidently saw the limits of partisanship. He was famously fast friends with the court's liberal elder stateswoman, Justice Ruth Bader Ginsburg, and, as Obama adviser David Axelrod recounted for CNN, lobbied for the appointment of another progressive, Elena Kagan, out of affection and admiration.