Either Vice President Kamala Harris or former President Donald Trump is weeks away from winning.Robert Gauthier/Los Angeles Times via Getty Images; Rebecca Noble/Getty ImagesStocks often struggle in September and October, especially in election years.The S&P 500 has broken that trend by soaring to record highs.Technical strategist David Keller shared how investors should position their portfolios.What should be the scariest time of year in markets is instead a full-blown celebration.US stocks usually fall in autumn.