By KEN SWEETNEW YORK (AP) — Stocks retreated for an eighth consecutive day on Thursday as nervous investors remain transfixed on the potential outcome of next week's U.S. presidential election, which has become too close to call. The stock market is now on its longest losing streak since the depths of the 2008 financial crisis. The Dow Jones industrial average dropped 28.97 points, or 0.2 percent, to 17,930.67. The Standard & Poor's 500 index lost 9.28 points, or 0.4 percent, to 2,088.66 and the Nasdaq composite index fell 47.16 points, or 0.9 percent, to 5,058.41. With five days left until the election, Hillary Clinton maintains a lead in national polling in the U.S. presidential race but Donald Trump has significantly narrowed the gap, particularly in swing states. Investors pointed to polls released in the last two days from Florida, New Hampshire and North Carolina where the two candidates are either statistically tied or Trump holds a small lead. Investors like certainty, which means they generally favor a Clinton victory as she is seen as maintaining the status quo. Trump's policies are less clear, and the uncertainty has caused jitters in financial markets. The last time the S&P 500 fell for eight straight days was early October 2008, the depths of the financial crisis. However the losses over this period have been modest, nowhere close to the losses racked up in 2008. "It's a pretty simple equation: uncertainty goes up, stock market goes down," said David Kelly, chief global strategist with JPMorgan Funds. The Mexican peso, which has become an indirect proxy among investors for Trump's chances at the White House, advanced 1 percent against the dollar on Thursday. Investors have speculated that a Trump administration would be negative for the Mexican economy, and would cause the Mexican peso's value to fall as a result.