First of all, I will assume Hillary doesn't run in 2016. Romney beat Obama and I have a feeling this would've scared the DNC into pushing Sanders forward so I will assume he becomes the nominee. Sanders runs a populist campaign, running against the more establishmentarian Romney. 2016 in real life but reversed. Sanders polls well in the Rust Belt but finds it difficult to make inroads in the South and Mountain West. The end result is similar to the real life 2004 result, but with Pennsylvania and Maine's 2nd district voting Republican as well. Sanders does well in the Upper Midwest but still struggles in Iowa and Ohio. Romney's more populist view on subsides in this scenario helps him barely snatch Iowa and also proves to be a big help in Ohio, which goes to Romney by 1%. Also, Maine's 2nd falls to Romney as Sanders' policies prove too much for upstate Maine. Virginia, North Carolina and Florida all go to Romney by over 5%. Sanders also loses out in Nevada, Colorado and New Mexico thanks to Romney doing a lot better among Hispanics in this scenario. Sanders does extremely well in New Hampshire, winning it by over 5% but he isn't as lucky in Pennsylvania which goes to Romney by about 3% thanks to doing rather poorly in the Philadelphia suburbs, losing Bucks, Monroe and Chester.
Final result: 313-225 Romney and Romney wins the popular vote by 3.
Romney: The Department of Agriculture uses subsidies to rationally manage food production. It would be foolish to reverse that policy.
Iowa Farmer: You know there's a certain panache to this answer that I find appealing.
