What is driving the stock market plunge?

• Besides risks to global supply chains, travel restrictions and profit warnings, many are seeing other dangers as part of a worsening economic picture.
• "The risk to the global consumer is the real problem. Starbucks and Apple can reopen their stores in China, but few people will go into them," said Michael O'Rourke, chief market strategist at JonesTrading.
• Uncertainty about the U.S. presidential election's outcome is also starting to drive markets, while even before the selloff this week, equities were being measured at lofty valuations.