[T]he evidence so far suggests Trump isn't taking advantage of that possibility. Four years ago, using a similar method to Cohn's, I argued that Mitt Romney could win with a lower percentage of whites in 2012 than many thought. Of course, Romney didn't pull it off; just because something is possible doesn't mean it will happen. And polls show Trump isn't in a stronger position than Romney to pull in enough white voters to win.1

Trump has trailed Hillary Clinton in every national poll for roughly the last three weeks. He's led in only three of 34 polls since knocking Ted Cruz and John Kasich from the race in early May. In fact, the only two pollsters who had Trump ahead and have released a more recent poll (Fox News and Rasmussen Reports) now show him trailing by 3 and 4 percentage points, respectively.

One big reason Trump is trailing -- by an average of 4 to 6 percentage points, depending on which aggregator you use -- is because, despite all the bluster, he isn't doing any better than Romney did among white voters. According to Cohn's estimate, based on pre-election surveys, Romney beat President Obama by 17 percentage points among white voters. To win, Trump would need to improve on Romney's margin by a minimum of 5 percentage points if the electorate looked exactly the same as it did in 2012 and every other racial group voted in the same manner as it did in 2012.