iStock; Rebecca Zisser/BIThe S&P 500's positive performance this year means that a Harris victory is likely, history says.The Misery Index, which tracks unemployment and inflation, is also down, pointing to a Harris win.However, market volatility and new employment data could change the narrative, strategists say.Historically, the stock market holds some clues about the outcome of the US presidential election.Typically, when the stock market rises, and unemployment and inflation remain low, the incumbent party remains in power.