A Four-Way Race?
It’s conceivable; if, as is certainly possible, if not probable, the Republican nominee is selected at a brokered convention, and if, as is almost certain, Hillary earns the Democratic nomination, both Donald Trump and Bernie Sanders have the financial resources and committed supporters to mount effective independent campaigns. What would result would be complete chaos and is entirely unpredictable. The question is, would Bernie do it? (I think most politicos would agree with me that it would be entirely unsurprising were Trump to do so).
Or could it get even more complicated if, say, Mitt Romney were to jump in and make it a five-way race?
Destructive Anachronism 