The fifth and sixth years of a presidency often end up being high noon for judicial politics. This time, the first confrontation concerns the powerful D.C. Circuit Court of Appeals, the venue for many important regulatory issues and a training ground for future Supreme Court justices.

On Tuesday, Republicans blocked the nomination of Cornelia Pillard to the court. Pillard’s was one of three nominations Republicans were opposing. They say the Democrats are trying to pack the court. The Democrats say they’re just trying to fill vacancies, and argue that the Republicans’ behavior is so abusive they’ll restrict the filibuster if it continues.

Republicans should remember what happened the last time we had such a fight, and they shouldn’t give in.

Starting in 2003, the Democratic minority embarked on an unprecedented series of filibusters to stop President George W. Bush’s appointments to appeals courts. Back then, Republicans said there was a crisis of judicial vacancies needing to be filled. Democrats replied that the courts, especially the D.C. Circuit, were underworked and that the Republicans were trying to pack the courts with like-minded judges. Now the sides are reversed, and so are the talking points.

As it happens, the Republicans have the better of the current argument. They aren’t conducting a “blockade” that violates past norms. President Barack Obama’s nominees are getting confirmed at a faster pace than Bush’s were at the same point in his presidency. One of Obama’s nominees, Sri Srinivasan, was unanimously confirmed in May.

And the D.C. Circuit now has even less work than it did when Democrats were blocking nominees. Merrick Garland, the court’s chief judge and an appointee of President Bill Clinton, informed the Senate that the number of oral arguments per active judge has fallen over the past decade. So have the number of written decisions issued and appeals taken.

Sen. Chuck Grassley, R-Iowa, says one judge on the circuit wrote to him to argue that “there wouldn’t be enough work to go around” if more were appointed. Grassley has introduced a bill that would shrink the circuit by three seats, and urges the administration to fill vacancies in other circuits.

I’ll let you in on a little secret: Nobody on either side of this debate actually cares about how big the circuit’s caseload is. What they care about is the court’s ideological balance.

Liberals say the D.C. Circuit has been making too many conservative rulings. It “has made decisions that have frustrated the president’s agenda,” complains Democratic legal activist Nan Aron. Jonathan Chait, of New York magazine, says today’s D.C. Circuit has been “one of the right’s most potent weapons during the Obama era.” And Sen. Chuck Schumer, D-N.Y., has complained about the court’s rulings on recess appointments and financial regulations, vowing that the new nominees will change its course.

The court is actually balanced between Democratic and Republican appointees. In recent testimony before the House Judiciary Committee, C. Boyden Gray noted that the court has been reversing the Obama administration’s regulatory actions at a lower rate than it did those of the Bush administration. Putting too much weight on such statistics is a mistake; the reasoning in the cases is more important. Yet when you look at the specifics, the Democratic indictment is even more off base.

Obama is the first president to make a recess appointment when the Senate said it wasn’t in recess; of course, the courts objected. In the financial case, the court merely said that the Securities and Exchange Commission had to follow the law about responding to public comments on a regulation’s costs and benefits before issuing it. As Adam White points out in the Weekly Standard, the court hasn’t touched regulations that followed the law.

One of the vacancies Democrats are trying to fill used to be held by John Roberts. After he became chief justice, Bush nominated the impeccably qualified Peter Keisler for the spot. The Democrats blocked him, and the seat has gone empty ever since. A reasonable case can be made against a minority party blocking judicial nominations, or for it. What can’t reasonably be argued is that Democrats should be able to use the tactic to keep a judgeship open until they have the power to fill it with a liberal, at which point Republicans have to stand down.

Republicans shouldn’t accept these rules. On this issue, the president’s agenda deserves to be frustrated.