“It’s no surprise that President Obama has been able to transform the ideological makeup of the courts — that happens when you have six years to pick judges and your party controls the Senate,” said Edward Whelan, the president of the Ethics and Public Policy Center, who was a senior official in the Justice Department under President George W. Bush. “The best way for conservative voters to prevent further damage to the courts is to swing the Senate to Republican control in the elections this November.”

Though the Obama administration was well on its way to leaving a lasting liberal legacy on the federal bench before Senate Democrats curbed the filibuster’s power, the rules change sped up the confirmation process. Today, the number of circuit judges appointed by Republican presidents is 77, compared with 95 by Democratic presidents, according to statistics kept by Russell R. Wheeler of the Brookings Institution.

At the beginning of Mr. Obama’s first term, the picture was reversed: 99 appointed by Republicans and 65 by Democrats. Of course, a president’s political affiliation ultimately has no bearing on how a judge decides cases. History is full of examples when partisans were disappointed by a judge who turned out not to be the loyal ally they expected, like David H. Souter, the liberal-leaning former Supreme Court justice nominated by the first President George Bush. The Supreme Court remains the only court that Republicans can still try to shape through using the filibuster. When Democrats changed the Senate rules to lower the threshold for most confirmations, they left one exception: The minority party still can require a 60-vote majority to confirm a justice.

The quickening pace of judicial confirmations is all the more surprising considering that at the end of his first term Mr. Obama was lagging well behind his two most immediate predecessors, Mr. Bush and Bill Clinton, in leaving an imprint on the courts. In part because his administration placed a higher priority on passing legislation like the Affordable Care Act than on confirming judges, Mr. Obama was slow to make nominations.

And early in his first term, the president purposely stayed away from nominating people who could be pilloried in the confirmation process as overly ideological and further strain partisan tensions in the Senate.