The Senate today confirmed Robert Wilkins to the U.S. Court of Appeals for the D.C. Circuit, marking the final step in an aggressive push from the White House and Senate Democrats to leave a mark on a key federal appeals court.

President Barack Obama in June simultaneously nominated Wilkins and two other lawyers—Patricia Millett and Cornelia Pillard—to the D.C. Circuit.

With Monday’s confirmation vote, Wilkins became the fourth Obama pick since May to take a seat on the D.C. Circuit. That matches the number of judges George W. Bush appointed to the appeals court, whose decisions in the regulatory arena—including securities, communications and the environment—have national sweep.

The Senate voted 55-43 to confirm Wilkins under a new streamlined confirmation process that came into place amid the partisan fight in the Senate over the D.C. Circuit. Wilkins will join the appeals court from the U.S. District Court for the District of Columbia, where he’s been a trial judge since 2010.

After Senate Republicans blocked Obama’s D.C. Circuit nominees from getting votes, Democrats changed longstanding Senate rules to strip the minority party of their rightto block nominee votes.

The Senate in December confirmed two other judges to the D.C. Circuit—Millett, a former Akin Gump Strauss Hauer & Feld partner and Pillard, who taught at Georgetown University Law Center.

Republicans argued that the D.C. Circuit workload did not justify the additional $1 million per year cost per judge. They accused Obama of filling the vacancies to “pack”the court in support of his legislative and regulatory proposals.

The confirmation of Obama’s D.C. Circuit picks shifts the balance of active judges from an even split—four Republican appointees and four Democratic appointees—toa 7-4 advantage for Democrats. Republican-appointed judges hold a 9-8 advantage when senior judges are counted.

Obama’s first successful appointment to the D.C. Circuit came in May, when the Senate confirmed former O’Melveny & Myers appellate partner Sri Srinivasan. He leftthe Justice Department Office of the Solicitor General to join the bench.

Wilkins’ confirmation came the same day that Miguel Estrada—unsuccessfully nominated to the D.C. Circuit under President George W. Bush—argued in the high court over the scope of the power of the president to use the recess appointment authority. (Democrats blocked Estrada’s nomination to the D.C. Circuit.)

Hours before the Wilkins vote, Estrada, co-chair of the appellate and constitutional law practice at Gibson, Dunn & Crutcher, argued a case on behalf of Senate Republicans that Obama overstepped his authority in making recess appointments to the National Labor Relations Board in 2012.

“It’s certainly interesting. Miguel Estrada is an extraordinary lawyer, and his own experience with the Senate certainly added significance to the situation as I saw it,” Sen. Mike Lee (R-Utah) said after watching the Supreme Court arguments. “This added a degree of poignancy that’s kind of intangible.”

The appointment of Wilkins opens up a vacancy on the federal trial bench in Washington.