McDowell's departure will open up one of the two spots reserved for Republicans on the five-member commission. Chairman Julius Genachowski is widely expected to step down sometime in the next few months. The White House often nominates Democratic and Republican commissioners as a pair to help ease confirmation through the Senate.
McDowell insisted that his announcement "is not a farewell," and said he has no plans other than taking his family on a "much needed vacation." He said he is consulting with the agency's ethics officer to ensure his departure is in compliance with ethics rules.
As a minority member of the commission, McDowell worked cooperatively with Genachowski and the other Democratic commissioners, but he dissented passionately from controversial decisions, such as net-neutrality regulations enacted in late 2010.
He has also repeatedly warned U.S. policymakers about the threat of international efforts to regulate the Internet.
"Rob McDowell has been an extraordinary colleague — deeply knowledgeable about the vital and growing communications and tech sector, creative, wise, and a great partner on the Commission," Genachowski said, adding that he was essential for "landmark reforms," including overhauling the multibillion-dollar Universal Service Fund and efforts to provide more frequencies for cellphone carriers.
McDowell would have been the leading candidate to take over the chairman's spot if Mitt Romney had been elected president.
—Updated at 12:40 p.m