U.S. stocks are entering a historically strong fourth quarter after the S&P 500 rose 12% in 2026 and remained less than 2% below its mid-August record high, while the Nasdaq Composite gained more than 15%. CFRA data show the S&P 500 has averaged a 4.2% fourth-quarter gain since 1945 and finished higher 85% of the time; fourth quarters in midterm years have averaged a 6.4% advance. The outlook faces a 5.34% 10-year Treasury yield, Federal Reserve policy decisions, demanding earnings comparisons, heavy artificial-intelligence capital spending and the November 3 elections that will determine control of Congress. Fundstrat Chief Investment Officer Tom Lee separately pointed to historical precedents supporting a potential fourth-quarter rally, while investors are watching whether AI hyperscalers revise their capital-expenditure plans.