The last of three presidential debates between President Barack Obama and Mitt Romney is scheduled for tonight from 9 p.m. at Lynn University in Boca Raton, Fla. Foreign policy is the subject and the 90-minute debate will be divided into six segments of approximately 15 minutes each. Moderator Bob Schieffer of CBS News will open each segment with a question, and each candidate will have two minutes to respond. The moderator will use the balance of the time in the segment for a discussion of the topic. The Commission on Presidential Debates, which sponsors the debates, says the topics could change because of news developments. Early today Obama campaign announced it was running a new television ad in the debate state of Florida with a rare focus on foreign policy. Most other television spots have been on economic and other domestic issues. The ad talked about the costs of the past decade of war over an image of a soldier with a prosthetic leg. It pointed out that Obama ended the war in Iraq and said Romney would have kept forces in the country longer to help with the transition. On Iran, senior Romney campaign foreign policy adviser Dan Senor said on NBC today that Romney's approach is that "we've got to reach a diplomatic solution." He said the Obama administration's policy on Iran for the past four years has not discouraged Tehran from moving forward with its nuclear ambitions.