There are only seven "toss-up" states in 2016.
According to Larry Sabato's "Crystal Ball," the Democratic nominee will start with 247 electoral votes while the Republican begins with 206. That means the Democrat needs just 23 more to win the White House while the Republican needs 64. However, even though the Democratic nominee starts with a sizeable head start, it's still a 50/50 election.
For the Democrats, a victory in 2016 entails zero expansion of the blue map, merely the limiting of blue-to-red transformations. Assuming the lean, likely, and safe Democratic states remain loyal to the party, the nominee need only win 23 of the 85 toss-up electoral votes. And if a lean Democratic state such as Wisconsin turns red, it is relatively easy to replace those votes with one or two toss-ups.
On the other hand, Republicans must hold all their usual states plus find a way to stitch together an additional 64 electoral votes, or 79 if they can’t hold North Carolina. To do this, the GOP candidate will have to come close to sweeping the toss-ups under most scenarios—a difficult task unless the election year’s fundamentals (President Obama’s job approval, economic conditions, war and peace, and so on) are moving powerfully against the Democrats.
If the Republican nominee loses either Florida or Ohio, there's no reasonable path to the win for them. On the other side, Democrats need to win Virginia or their way forward becomes much murkier.