By a nearly 2 to 1 margin, Americans support the notion of striking a deal with Iran that restricts the nation’s nuclear program in exchange for loosening sanctions, a new Washington Post-ABC News poll finds. But the survey — released hours before Tuesday’s negotiating deadline — also finds few Americans are hopeful that such an agreement will be effective. Nearly six in 10 say they are not confident that a deal will prevent Iran from developing nuclear weapons, unchanged from 15 months ago, when the United States, France, Britain, Germany, China and Russia reached an interim agreement with Iran aimed...