The S&P 500 historically shows weaker returns in the first year of a presidential term, with an average annual return of 6.6%, below the 10% historical average. A missed Santa Rally this year, where the index dropped 0.53%, suggests a negative January could lead to further declines, as historically, a negative January results in a 70% chance of a negative full year. Despite this, the market's response to Trump's re-election may challenge historical trends, though concerns about overvalued stocks persist.