President Obama ’s chief negotiator with Iran , Wendy R. Sherman, said on Wednesday that she planned to leave the administration shortly after the June 30 deadline for a final deal on limiting the country’s nuclear program . “It’s been two long years,” Ms. Sherman, the under secretary of state for policy, said in her office on Wednesday. With her departure, all the top officials who have negotiated with Iran over those two years will have left the administration, leaving questions about who will coordinate the complex process of carrying out a deal if one is struck by the deadline. On Wednesday night, Secretary of State John Kerry, who has relied on Ms. Sherman to conduct the high-stakes negotiations, said that her “mentoring of colleagues, her experience, her passion for diplomacy, her calm in the storm set her apart as a great under secretary of state.” Her […]