For politics fans, it’s easy to get caught up in fun Electoral College scenarios — ones in which small states make a big difference or in which the House of Representatives has to decide the election. The alternative — endlessly repeating that “Florida is important; Ohio is important” — can get tiresome. That said, Ohio is important, and Florida is super important.

Florida has a 19 percent chance of providing the decisive vote in the Electoral College according to our polls-only forecast. It’s the most likely “tipping-point state,” in FiveThirtyEight parlance. That’s up from 16 percent just two weeks ago. There’s only one other state with a better than 10 percent chance of casting the decisive electoral vote: Pennsylvania, at 12 percent.

Florida tends to be a crucial battleground state in presidential elections (more on this in a moment), but it’s become even more pivotal in recent weeks in the race between Hillary Clinton and Donald Trump. Clinton has improved her position nationally and in Florida, but she’s made a bit more progress in the Sunshine State, moving it closer to the national average. Clinton leads by about 3 percentage points nationally and by about 1 point in Florida. That’s made it more plausible that Clinton could hold onto Florida while losing some light-blue states.

Let’s say, for example, that on Election Day, Clinton underperforms with white voters without college degrees even more so than she is doing now. Her support would collapse in the Midwest, and her troubles in Maine would likely bleed over into New Hampshire. But Florida is more diverse, with one of the largest groups of Latino voters of any battleground state and a sizable African-American population. So, in this scenario, the nonwhite vote in Florida might allow Clinton to hold onto the state even if she were to lose Michigan, New Hampshire, Ohio and Wisconsin.

And that’s a winning map:

If Clinton wins Florida, Michigan and New Hampshire, she can afford to lose Pennsylvania, where she’s held a lead even as she’s trailed Trump in next-door Ohio.

Indeed, winning Florida opens up so many electoral paths for Clinton that it’s probably a must-win for Trump. If he loses Florida, Trump wins the presidency only 5 percent of the time according to our polls-only forecast. (Clinton, on the other hand, wins the election 33 percent of the time without a victory in Florida.) Considering that Clinton has led in every post-debate survey in Florida and has a small lead there in our polls-only forecast, you can understand why Clinton is currently a favorite to win the election.

Florida has two basic things going for it that make it so pivotal. The first, as I mentioned, is how closely the state mirrors the national vote. It’s about 2 or 3 percentage points more Republican-leaning than the country at the moment. Nevada and Wisconsin are about as equally close to the national margin, and the only states closer are Colorado (the current tipping-point state according to our forecasts), New Hampshire and Pennsylvania. Considering that the election is a little more than a month away and the inherent error in any forecast, it’s possible that the vote margin in Florida ends up as close or closer as in these other states.

The other factor that makes Florida important is its large population. None of the states listed in the previous paragraph besides Florida has more than 20 electoral votes. Florida has 29. It’s possible, therefore, for a candidate to lose smaller swing states and make up for those losses by winning in Florida.

No single state guarantees victory. The notion of a “must-win” state tends to be overplayed — instead, the states tend to move in concert, and the winner of the national popular vote almost always wins in the Electoral College. But Florida is about as close to an all-important state as we’re likely to see.





FiveThirtyEight: Election forecast update – Oct. 3, 2016