U.S. Federal Trade Commission Chairman Jon Leibowitz’s departure will sharpen an already spirited succession battle. (Alex Wong/GETTY IMAGES)

Federal Trade Commission Chairman Jon Leibowitz on Friday announcedplans to leave the agency, sharpening an already spirited succession battle and potentially opening an awkward transition period for an agency on the forefront of consumer protection.

“We have made significant strides,” Leibowitz said in an interview late Thursday, confirming his plan to resign from the FTC, effective in mid-February. “It’s a good time to leave.”

The departure of Leibowitz, a Democrat who joined the commission in 2004 and became its chairman in 2009, has been widely rumored for months. Two other Democrats on the commission, Julie Brill and Edith Ramirez, are among several leading candidates to fill the chairmanship.

The transition to a new chairman — whether from within the commission or from outside — will create at least a temporary partisan split, with two Democrats, two Republicans and one seat empty until President Obama can gain confirmation for a nominee. Such 2 to 2 divides on the five-member commission are not uncommon during transitions, but they can make it difficult to chart a forceful path for the FTC.

“It’s a complication when you have four [commissioners], no doubt,” said former FTC chairman William Kovacic, a law professor at George Washington University. “It can limit what you do severely.”

The last such transition period lasted two years, from 2008 to 2010. It could take several months for Obama to gain confirmation for a new FTC commissioner, because of the highly partisan atmosphere on Capitol Hill.

Leibowitz called such concerns overblown because of the agency’s record of operating across party lines. “We have been a largely functional agency in an often dysfunctional Washington,” he said. “I think we have done our job the way we are supposed to, and in a consensus-driven way.”

Sen. Amy Klobuchar (D-Minn.), the new chairman of the Judiciary Committee’s antitrust subcommittee, praised Leibo­witz’s record and bipartisan style but expressed some concern about the coming transition. “I hope this legacy of bipartisanship carries through during this period,” she said.

Leibowitz is departing with a reputation as a collegial leader who took forceful stands on health-care matters while raising the agency’s profile on high-tech issues. Under Leibowitz and David Vladeck, a Georgetown University law professor who was his top consumer-protection deputy, the FTC became the government’s leading overseer of Silicon Valley, with enforcement actions against Facebook, Intel and Google.

The FTC’s handling of antitrust complaints against Google, which ended with modest concessions in January, sparked criticism, especially over the aggressive way the agency lobbied for the case two years ago and raised expectations of a major action before eventually ruling out a legal showdown with the Internet search giant. Former commissioner J. Thomas Rosch, a Republican who recently retired, wrote tartly in a dissent, “After promising an elephant more than a year ago, the commission has instead brought forth a couple of mice.”

Leibowitz’s overall record on antitrust matters also drew grumbling from some consumer advocates, who longed for more aggressive intervention and considered Leibowitz too eager to seek settlements instead of legal action. He said in the interview that he preferred a “light touch” in fast-moving industries, such as technology, in which regulatory action can be overtaken by changes in business conditions.

Leibowitz’s term is likely to be remembered for its energetic approach to consumer protection, especially in technology. He pushed for new protections for children online, hired the FTC’s first technologists and oversaw the creation of its first lab for testing mobile devices. A new mobile privacy policy is due to be released Friday.

Even those who sometimes complained that the FTC didn’t go far enough in punishing companies that violated privacy policies were glad to see the subject taking a central role within the agency.

“All of a sudden the FTC became relevant again, and not just a sleepy backwater that yawned as consumers got ripped off,” said Jeff Chester, executive director of the Center for Digital Democracy. “Leibowitz has made some positive moves, but much more needs to be done.”

Aside from Brill and Ramirez, the list of potential new chairmen includes the director of the FTC’s Bureau of Economics, Howard A. Shelanski, Justice Department lawyer Leslie C. Overton and University of Colorado Law School Dean Philip J. Weiser, people who follow the agency said.

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