"Investors are clinging to the positives," Bell said, pointing to rate easing hopes and signs of economic resilience from recent releases including housing market and consumer spending data. Historically speaking, government shutdowns are brief and they don't have an impact on profitability so investors tend to be forward-looking," said McKinney. Investors were also monitoring Fed policymakers' commentary for any signs of concern over the potential loss of economic visibility should a shutdown materialize. AppLovin set a fresh record high, also providing one of the biggest lifts for the S&P 500. After U.S. President Donald Trump shared a video on Sunday promoting the health benefits of hemp-derived cannabidiol, U.S.-listed shares of cannabis-related companies rose.