Question is how did Obama's first term go and what kind of campaigns both candidates run? For sure you'd have to assume Obama has the upper hand due to incumbency and a strong charisma factor on his side.
Not sure who would have been Obama's VP here; very doubtful it's Biden, and Kaine was running for senate in 2012. I'm saying Jack Reed here. Would have made sense as VP selection in 2012, and for sure kept on the ticket 4 years later.
✓ President Barack Obama (D-IL)/Vice President Jack Reed (D-RI): 323 EVs.; 51.0%Mr. Donald J. Trump (R-NY)/Governor Mike Pence (R-IN): 215 EVs.; 46.2%Btw, would have been an interesting timeline, with 3 Bush presidents, all going down after a single term in their reelection bids.