Up until just recently, the Nasdaq Composite was enjoying a wide lead against the S&P 500 in terms of 2012 performance. That lead has evaporated over the last two weeks since earnings season began. Including today's big decline, the Nasdaq is now outperforming the S&P 500 by just 1.35 percentage points in 2012. Will the lead soon flip to a lag? At this rate, it could be lagging by the end of the trading day.