The U.S. presidential race has reached a critical juncture. The Republicans have a confirmed nominee in John McCain; as for the Democrats Hillary Clinton has bounced back while Barack Obama retains a marginal lead in terms of delegates. How the presidential race evolves will be shaped in part by the increasingly worrisome state of the U.S. economy. Though it has not yet gone through two consecutive quarters of negative growth -- the common definition of a recession -- signs of a slowdown are evident everywhere. What lies ahead for the U.S. and world economies? What is the right strategy for investors in this environment? Knowledge at Wharton discussed these questions and more with finance professor Jeremy Siegel author of The Future for Investors.