President Obama's nominee to be U.S. ambassador to Iraq, Brett McGurk, has withdrawn his nomination amidst questions about his professionalism and experience.

Some on Capitol Hill already had questions about McGurk, a former National Security Council staffer for both President George W. Bush and President Obama, given his lack of managerial experience and role in negotiations with Iraq that ended with the United States withdrawing all combat troops.

It seemed McGurk might weather those criticisms, but earlier this month someone leaked emails he sent in 2008 while in Iraq, ones in which he wooed a female Wall Street Journal reporter - perhaps jokingly referencing favors of access and information. He later divorced his wife and married the reporter. Senators wanted to question McGurk about suggestions in the emails, jokingly or otherwise, that he would give a reporter access to sensitive information and power if their relationship blossomed.

Tommy Vietor, a spokesman for the National Security Council, said in a statement: "We greatly appreciate Brett's years of service on behalf of the United States, to include tireless and effective leadership in Iraq from the height of the war to the moment our last troops left Iraq in December and through the challenging transition earlier this year. He served in two administrations, and his commitment to the national interest and to the mission was always clear. He has proven himself to be a skilled diplomat willing to take on some of the toughest challenges at the toughest times in a difficult region. While we regret to see Brett withdraw his candidacy there is no doubt that he will be called on again to serve the country."

Last week, six Republican senators on the Foreign Relations Committee asked the president to withdraw McGurk's nomination. White House press secretary Jay Carney said in response that "the president put forward this nominee because he is qualified for the job and will serve ably when he's confirmed."

- Jake Tapper