Wall Street's Midterm Cheat Sheet: The Likeliest Outcome Is The Worst For Stocks

Prediction markets heading into Tuesday's midterms have Democrats at a 66% chance of taking both the House and the Senate, according to JPMorgan's Market Intelligence desk, which pulled the odds from Bloomberg's prediction market data as of Nov. 1. A Blue Wave is also the exact scenario in which JPM's range for the S&P 500 includes a decline.

Democrat odds have basically snowballed over the past few months. When we last checked JPMorgan's numbers in early October, a Democratic sweep stood at 62% and a Democratic House with a Republican Senate at 29%. The split is now 26%, with a Republican hold of both chambers at 7% and a GOP House paired with a Democratic Senate at 1%.