WHEN CAITLIN J. HALLIGAN was nominated in 2010 to a seat on the U.S. Court of Appeals for the D.C. Circuit, the prestigious 11-member court had two vacancies. Today, there are three, after Judge Douglas H. Ginsburg took senior status this fall.

Yet some Senate Republicans argue that there is no need to install Ms. Halligan because the court’s caseload has shrunk. Others look suspiciously on her purported views on antiterrorism policy. GOP senators are grasping at straws to block Ms. Halligan’s ascension, perhaps in hopes of preserving the vacancy for a Republican president to fill. These lawmakers rightly objected to such tactics when deployed by Democrats to stall or defeat well-qualified Republican nominees; they should not revert to them now when a Democrat controls the White House.

Ms. Halligan has had a distinguished career and deserves to be confirmed. A graduate of the Georgetown University Law Center, she clerked for D.C. Circuit Judge Patricia M. Wald and later for Supreme Court Justice Stephen Breyer. She has served as head of the appellate practice at a top New York law firm, as solicitor general in that state and now as general counsel for the New York County District Attorney’s Office in Manhattan. The American Bar Association gave Ms. Halligan a unanimous well-qualified rating. The Senate Judiciary Committee approved her nomination seven months ago; she has been waiting for a floor vote ever since.

While it is true that caseloads have been inching downward at the D.C. Circuit, the decline does not take into account the complexity and scope of the cases that land at the court. They include direct appeals involving federal regulatory decisions and national security matters, including cases stemming from the detentions at the U.S. naval base in Guantanamo Bay, Cuba.

Critics note that Ms. Halligan’s name appears on a 2004 report by the New York City Bar Association that lambasted the Bush administration for asserting the legal authority to hold enemy combatants without trial until the cessation of hostilities; the Supreme Court ultimately endorsed the administration’s position. Ms. Halligan acknowledges that she was a member of the committee that wrote the report but testified that she was not involved in its development or writing and said she learned of it only in 2010, while gathering material for the confirmation process. Ms. Halligan testified that she did not agree with the report’s conclusions.

Some critics suggest that Ms. Halligan’s repudiation is a “confirmation conversion.” Yet no evidence to dispute her account has emerged during the eight months since her hearing. The report episode is odd but should not disqualify Ms. Halligan, given the mountain of evidence that she is a smart and well-qualified candidate.