CAITLIN J. HALLIGAN has been waiting to become a federal circuit judge ever since President Obama nominated her — in 2010. Since then, she has languished in Senate confirmation hell, repeatedly renominated but refused a simple up-or-down vote. On Wednesday, Democrats tried to break the unjustifiable impasse. Once again, Republicans successfully filibustered, denying a qualified nominee a fair shot at a seat on the bench and leaving the U.S. Court of Appeals for the D.C. Circuit short-staffed.

The GOP’s abuse of the filibuster is bad for the country, for many of the reasons Republicans were eager to spell out when Democrats unfairly blocked President George W. Bush’s judicial nominees. Since the last time Ms. Halligan faced a GOP filibuster, the D.C. Circuit has lost another judge, leaving four vacancies. Yet it is the forum for some of the nation’s weightiest legal disputes, involving a wide range of federal matters — from Environmental Protection Agency regulations to detentions at the Guantanamo Bay naval base.

That, Republicans argue, is one reason to keep Ms. Halligan away from the bench: The D.C. Circuit is simply too important to offer an “activist” such as her a lifetime appointment. Among other things, they point to her time as solicitor general of New York, whenshe defended in appellate court a lawsuit that then-state Attorney General Eliot Spitzer had brought against gunmakers. New York lost its case. But her role in it says little about her views on the Second Amendment or whether she would be an activist judge in other areas. Mr. Spitzer was the one who decided to pursue that case. If it were fair to ascribe the views of clients to the lawyers who represent them, many members of Congress would no doubt have trouble explaining themselves.

Against the distorted view of Ms. Halligan’s record that Republicans have offered stand the endorsements of prominent legal minds both liberal and conservative, a unanimous well-qualified rating from the American Bar Association and a storied career in public service and private practice.

On balance, Ms. Halligan’s record doesn’t come close to justifying what should be an extraordinary resort, filibustering a judicial nominee. That’s a standard that not only we believe in; it’s also one endorsed in 2005 by a group of senators known as the “Gang of 14.” Yet three of those senators — Susan Collins (R-Maine), Lindsey O. Graham (R-S.C.) and John McCain (R-Ariz.) — voted to sustain Wednesday’s filibuster against Ms. Halligan.

The Senate recently started to reform itself, removing procedures that unnecessarily eat up time. But the Halligan filibuster shows that the spirit of that reform has hardly taken root. When lawmakers hold nominees hostage to politics and ideology, trampling the legitimate prerogative of the president to staff the government and the judiciary, it degrades the effectiveness of government and the courts, deters qualified people from pursuing public service and poisons the politics in Washington.