The race for the Democratic nomination looks much like it did a year ago—but previous contests prove that once voting starts, momentum can reshuffle the pack. Iran has been roiling with protests following the accidental downing of an airliner; what should Iranians and the wider world expect now? And we examine how Bogotá’s once-adored public-transport system went so wrong. For full access to print, digital and audio editions of The Economist, subscribe here www.economist.com/radiooffer