When I talk to Democrats about the presidential primary, I hear the same thing over and over: “I’ll vote for whoever I think can beat Donald Trump.”

Fair enough. The problem is that there’s no way to know for sure who that might be. The latest polls show all of the top Democratic Party presidential candidates beating Trump in a general election. But then, these same polls also showed Hillary Clinton beating Trump, so who can trust them? In order to figure out who has the best chance of beating Trump, we’ll need to reason it out.

Electorally speaking, Trump won for two related reasons: in key swing states, a handful of former Obama voters opted for Trump over Clinton, and another handful decided to vote for nobody at all. To unseat Trump, the nominee will have to perform well in those swing areas. Instead of projecting our own fantasies about what voters (and potential voters) are looking for in a candidate, we should look at the supporter data that is already available.