Over the past two decades, Americans have grown increasingly polarized in their politics — and the states have followed a similar trend. As the chart above shows, the state-by-state spread of the margins separating the vote for the Republican and Democratic presidential candidates widened from 1992 to 2012. In 1992, Bill Clinton’s biggest win1 was in Massachusetts, where he prevailed by 18.5 percentage points. His biggest loss was in Utah, by 18.7 points. If you adjust those numbers by his national popular vote margin — which was 5.6 points — you get D+13 for Massachusetts and R+24 for Utah, a total spread of about 37 points. The total spread in 2012, by contrast was 91 points: from Utah’s R+52 to Hawaii’s D+39.
In other words, from 1992 to 2012, blue states grew a bit bluer, red states a bit redder and tossup states a bit fewer in number.
But 2016 seems to be bucking that trend: Electoral margins look more tightly distributed across states than they have in recent elections. (We don’t know how the country is going to vote, of course, so for 2016, we’re looking at the difference in Hillary Clinton’s and Donald Trump’s polling average in each state on Aug. 29 and adjusting them relative to our polls-only forecastfor the national popular vote.) But there are two big caveats here: Wyoming and Hawaii. Because they are so solidly partisan, we don’t have polling numbers for those states (they’re boring), so we can’t place them within our 2016 distribution above. But they would undoubtedly increase the spread of that distribution, again because Wyoming is so red and Hawaii so blue.
The total spread between states isn’t all that matters, of course — more important for the outcome of the election is the number of states where we expect margins to be close (in an absolute sense, not just relative to the national result). This year, in addition to having less of a spread, has more states with closer absolute margins than other recent elections. In 2008, for example, only six states had electoral margins of 5 percentage points or less; this year, our polling averages show 11 states as being that close.
Part of the reason there are more competitive states this year is that Trump is nudging some red states into the tossup zone while outperforming past GOP nominees in some blue states. But it’s important to keep in mind that overall, the electoral map isn’t changing dramatically in 2016: If you take state results from 2012 in the chart above and adjust them for how the country has shifted as a whole at this point in the cycle, you’ll have a pretty accurate picture of where each state stands currently.
Ritchie King is senior editor for data visualization at FiveThirtyEight.