They absolutely need each other in their attempt for leadership. Piggy needs Ralph's charisma and natural leadership, and Ralph needs Piggy's rationale and intelligence. However, Ralph also recognized the downfalls of Piggy(physical appearance, un-usable ideas) and didn't always trust what Piggy had to say.
One of my students last year paralleled President Bush and VP Cheney to Ralph and Piggy. At the risk of starting a political argument, that's probably not a bad example...
