Now, why would you want that?
One of the ways to make sense of what's going on in an election in real time is to see how key counties compare to earlier elections. So if you're watching Florida, for instance, and there are only 20% of precincts reporting statewide you can look at how Clinton or Trump are doing in certain counties relative to how Obama and Romney did in 2012. This is particularly valuable for bellwether counties. If you see Clinton significantly underperforming Obama's numbers, that's obviously a bad sign or vice versa.
In every previous election I've covered people are often calling up this data from various sources, hunting it down from around the web. The real pros know from memory what numbers a Democrat or Republican needs in a given county to win a state or congressional district. We thought it would be handy to have the most relevant data - the 2012 presidential election right there at your fingertips (or, I guess, mouse clicks).