Nate Cohn, The Upshot/New York Times

Forget the Koch Brothers or Super PACs or even President. The most-watched player in the 2014 Midterms just might be a computer program called LEO.LEO is the always-on, data-crunching, poll-adjusting Senate forecasting model used by the New York Times. Each day LEO takes the latest polls and historical data from around the country, blends in other information like fundraising and national polling, and then simulates all 36 Senate races – 250,000 times. And from that, each day LEO speaks about which party will win the Midterm’s grand prize – U.S. Senate control.So following several big weeks of primary voting, what does LEO have to say… and why should we believe it?Nate Cohn is a reporter at the New York Times’ new hot spot – The Upshot – where he covers elections, polling and demographics…