Sestak failed to qualify for any of the debates sponsored this year by the Democratic Party. The Associated Press reported he recently finished a walk across New Hampshire intended to draw interest to his campaign.
"Without the privilege of national press, it is unfair to ask others to husband their resolve and to sacrifice resources any longer," Sestak said. "I deeply appreciate the support so many of you offered -- whether by volunteering, offering financial contributions or coming to our campaign events. I will miss the opportunities I had in experiencing America in such a wonderful way!"
Sestak, 67, spent more than three decades in the Navy and served two terms representing Pennsylvania's 7th Congressional District in the House, from 2007 to 2011. In 2010, he challenged Sen. Arlen Specter in the Democratic primary. He won the nomination but went on to lose to Republican Pat Toomey in the general election.