Most economists believe the U.S. Federal Reserve has almost done enough to cure America's inflation challenges, but there is a small probability of one more interest rate hike in November. If that happens, more investors will likely turn to stocks as they hunt for higher returns, and companies will be able to borrow money at cheaper interest rates to fuel growth. However, if rates remain higher for longer -- or worse, the Fed increases them more than expected -- the reverse could happen, which will create a headwind for the stock market.