Editor's note: David Frum writes a weekly column for CNN.com. A special assistant to President Bush in 2001-2, he is the author of six books, including "Comeback: Conservatism That Can Win Again" and the editor of FrumForum.
(CNN) -- Party of no? When it comes to Supreme Court nominations, the GOP is a flock of baby lambs compared with their opposites on the Democratic side.
The past two Democratic presidents have named three justices between them: Sonia Sotomayor, Stephen Breyer and Ruth Bader Ginsburg. All glided painlessly to confirmation.
Compare that with the mayhem inflicted on Republican choices. Two of President Nixon's nominees were rejected by the Senate. Ditto for one of Ronald Reagan's choices (another withdrew shortly after he was nominated). One of President George H.W. Bush's choices, Clarence Thomas, was confirmed after a fight that still ranks as perhaps the most vicious in confirmation history.
It's hard to argue that the difference is due to the superior quality of the Democratic choices. Ginsburg's views were and are at least as controversial as Robert Bork's. Not only Bork, but two other Republican nominees (Clement Haynsworth and Douglas Ginsburg) could show legal credentials that brightly outshone Sotomayor's.
Nor is it just a matter of clout: Although Republicans lacked the votes to defeat Ruth Bader Ginsburg, Breyer and Sotomayor, they could have filibustered either of the first two.
No, the difference is not in the nominees. It is in the parties. On judges, Republicans have played by softer rules than Democrats. There's no Republican equivalent of the notoriously scurrilous 1987 speech of Sen. Edward Kennedy's against Bork:
"Robert Bork's America is a land in which women would be forced into back-alley abortions, blacks would sit at segregated lunch counters, rogue police could break down citizens' doors in midnight raids, schoolchildren could not be taught about evolution, writers and artists would be censored at the whim of government, and the doors of the federal courts would be shut on the fingers of millions of citizens for whom the judiciary is often the only protector of the individual rights that are the heart of our democracy."
It's not as if Republicans do not know how to play rough when they wish to do so. But on judges, Republicans have not wished to play rough.
Why not? Republicans have won seven of the 11 presidential elections since 1968. Over those same years, Republican presidents made a total of 11 appointments to the high court, with the nominees becoming steadily more conservative over time.
Democrats fought back, using every weapon at hand, including the very nasty weapons deployed against Bork and Thomas. And Republicans counterattacked, by emphasizing the legitimate right of election winners to choose judges who reflected majority values.
There's an old saying: "Where you stand depends on where you sit." It's also true however that parties take some time to realize that they are sitting in a new place.
The Republican senators who deferred to President Clinton's nominations had argued for years that it was inappropriate for senators to vote against a judge merely because they disagreed with a judge's legal philosophy. Those senators would not and could not abruptly reverse themselves.
But what people cannot do immediately, they can learn to do after a time. Republicans voted for Ruth Bader Ginsburg and Breyer to send a message about how Thomas and Bork should have been treated -- and to lay down markers for how Republican judges should be treated in the future. But those votes, like the Sotomayor vote, occurred in the immediate aftermath of a Democratic presidential victory following many years of Republican administration. They do not necessarily foretell the future.
As Republicans settle into opposition, they may begin to think and feel like an opposition. They may lose the practice of deference, forget their objections to the filibuster of judicial nominations.
President Obama's next nominee can probably expect the same easy time that Ginsburg and Breyer enjoyed. But if there are more nominations in a hypothetical Obama second term, they may discover themselves haunted by Kennedy's malign precedent and Thomas' brutal ordeal.
The opinions expressed in this commentary are solely those of David Frum.