Washington ? President Barack Obama’s second nominee for transportation security chief withdrew from consideration Friday because of questions over his background as a defense contractor.

Retired Army Maj. Gen. Robert Harding took himself out of the running as head of the Transportation Security Administration, another setback for Obama after his first choice withdrew in January because he faced a tough confirmation struggle in Congress. The Obama administration has called the job the most important unfilled position on Obama’s team.

“I feel that the distractions caused by my work as a defense contractor would not be good for this administration nor for the Department of Homeland Security,” Harding said in a late-evening statement released by the White House. The agency is part of Homeland Security.