From an April 9 National Review Online editorial:

Replacing Justice Stevens

The question for conservatives will be not whether but how to oppose Obama's nominee.

[...]

No doubt some Republicans will say that it is unimportant to fight the nominee because Obama will merely be replacing one liberal with another rather than changing the balance of the Court. But the choice before any Republican senator is whether to acquiesce to several more decades of liberal activism on the bench. Unless Obama provides evidence of having dropped his litmus tests, the question for conservatives will be not whether but how to oppose Obama's nominee.

It is highly unlikely that Republicans will be able to deny that nominee an up-or-down vote, and any attempt to do so will probably backfire. But Republicans are nonetheless in a position of strength. Even last year - well before the midterm elections, with Obama more popular than he is today, and dealing with the first Latina nominee - Republicans were able to force the debate over Sonia Sotomayor's nomination to take place along conservative lines. This year, Republicans should again make the case against judicial liberalism, both in principle and in practice, and then vote accordingly.