(CBS) CAIRO - There are many opposition groups in Egypt. None is as organized or as vilified as the Muslim Brotherhood. On Friday, its leaders said they won't run a candidate for president, but the brotherhood does expect to play a role in Egypt's future, CBS News Correspondent Mark Strassmann reports. Long before the clamor of Tahrir Square, Hosni Mubarak heard one group's dissent and despised them for it. They're the Muslim Brotherhood, religious conservatives, often secretive and poorly understood. What is clear: They want an Egyptian Islamic state. This week, they stepped out of the shadows and joined the...