When George W. Bush nominated Alito in 2006, even his allies nicknamed him "Scalito," as if the Italian-American justice was sure to be a kind of federalist Mini-me. Superficially, Scalia and Alito seemed to be similar -- both natives of the New York region, both products of Catholic families, both former executive-branch lawyers for Republican presidents, and, most important, both holders of unimpeachable conservative credentials.

But Alito has become a kind of un-Scalia. Scalia is an "originalist"; in deciding constitutional cases, he reads the Big History Book and tells the rest of us the "original public meaning" of the Constitution. Originalism, even though it flourishes in the twenty-first century academe, was originally a political movement, invented during the Reagan years as a club to berate "activist" judges who voted for reproductive rights or limits on the death penalty. It has succeeded so well that it is now entering the final stage of Hollywood Fame. (1. What's Originalism? 2. Get me an Originalist. 3. Get me an Originalist type. 4. What's Originalism?) And "Scalito" is not only not Mini-me, he's not an originalist at all.

During argument in Brown v. Entertainment Merchants Association (the "violent video games" case), Alito interrupted a Scalia question to say, "I think what Justice Scalia wants to know is what James Madison thought about video games. Did he enjoy them?" In United States v. Jones, in which the issue was whether placing a GPS tracking device on a suspect's car is a "search" within the meaning of the Fourteenth Amendment, Alito wrote separately to ridicule Scalia's turn to the common law of the Georgian era to decide a case about computerized earth-satellite data. "Is it possible to imagine a case in which a constable secreted himself somewhere in a coach and remained there for a period of time in order to monitor the movements of the coach's owner?" he wrote.

Both justices are very conservative. But Scalia's conservatism looks back, invoking the spirits of the Framers. Alito's is forward-looking. He frequently discusses the dystopian implications of modern technology -- whether it be GPS trackers, the Internet, video games, or violent pornography and "crush" videos. Scalia asks how things were done in the past, because the past was good; Alito asks how they should be done in the future, lest the future be bad. Scalia talks about principles; Alito talks about consequences. If this were not a mean thing to say about a conservative, one would call Alito a pragmatist, the Stephen Breyer of the right.

If Alito does become the agenda-setter (by no means a sure thing), how would doctrine differ? Both men are rigidly opposed to affirmative action; neither seems to have the slightest patience for gay rights. They do differ sharply on the First Amendment. Both follow the strand of conservative judicial thought -- illustrated in a recent article by Temple law professor David Kairys -- that the First Amendment exists to empower the powerful rather than offer voice to the lowly. But Scalia is swayed by historical precedent to defend the speech of those he dislikes; Alito, outside the campaign-finance area, rarely meets a restriction on "distasteful" speech -- by funeral protesters, gay-rights advocates, or purveyors of dog-fight videos -- that he does not embrace.