It has been said that Texas is a “non-voting state,” and this has been particularly true of midterm elections where turnout as a percentage of eligible voters has only occasionally reached even 30 percent over the last century. In 2018, turnout skyrocketed to 46 percent of citizens of voting age.

In many states, or nationwide, a 46 percent turnout rate would be high, but not all that remarkable. In Texas, it was a higher turnout rate than in six of the last ten presidential elections.

The chart shows turnout rates as a percentage of citizens of voting age in every election in Texas from 1900 to 2018. In addition to the pretty stark effects of things like poll taxes in the early 20th century, the other thing that becomes clear is that 2018 “looks” like a presidential year rather than like a part of the series of midterms.

Why was turnout so high?

The emerging picture of Texas suggests several reasons for the increase in turnout:

The same forces that drove higher-than-normal national turnout were also at play in Texas: Democrats were intensely engaged throughout the cycle because of their opposition to President Trump, while Republican intensity surged in the wake of the Brett Kavanaugh U.S. Supreme Court confirmation fight. This was the first midterm in years where candidates from the two major parties competed in a close top-of-ticket statewide race, with the most recent perhaps being the lieutenant governor’s race between David Dewhurst and John Sharp in 2002. Beto O’Rourke’s paid voter contact efforts and significant earned media served to boost Democratic enthusiasm and ultimately participation. Both Republicans and Democrats executed sophisticated, and effective, field programs. Republican Gov. Greg Abbott’s campaign built a sizeable voter contact effort with field operatives throughout the state. And O’Rourke matched the size of this effort with a real, data-driven field program that turned out infrequent but Democratic-leaning voters.

With the benefit of hindsight, it is perhaps unsurprising that turnout in Texas in 2018 looked more like a presidential year than a midterm. The campaigns themselves more closely represented a presidential level of sophistication that yielded an increase in earned media, voter interest, spending, and grassroots organization than in previous Texas midterms.

What comes next?

We’re already being asked what we think 2020 turnout in Texas might look like. The only honest answer is “it depends.”

There is a plausible scenario in which the turnout rate in 2020 sets a modern presidential-year record. Another falls more in line with typical presidential years, a few points above or below 2016 turnout rates.

We did not know in January of 2017 quite how the Trump presidency would unfold, that O’Rourke would raise unprecedented sums of money and run a competitive Senate campaign with huge paid and earned media, or that a pattern of external events (Kavanaugh, pipe bombs, etc.) would all be part of the eventual turnout picture in 2018.

Similarly, we just don’t know what will happen between now and 2020. Here are some factors to watch:

How competitive is the presidential race nationally? A highly competitive race will boost turnout; a landslide by either side won’t.

To what extent does the Democratic nominee energize Texans (for or against)? A nominee like O’Rourke or Julian Castro would boost turnout in Texas and make a record-setting election more likely. Out-of-staters like Elizabeth Warren or Joe Biden would likely not have the same effect.

What does the electoral map look like, and how do the campaigns spend their money? If contestants see Texas as “in play,” there will probably be more money and organization in the state, boosting turnout. If the states that will determine the electoral outcome are the same as in 2016, then Texas could see less effort than it did in the 2018 elections.

What will the external environment be like in 2020? Will the economy be booming or in recession? Will we be at war somewhere?

How competitive is any potential challenge to U.S. Sen. John Cornyn, who has said he will be seeking reelection?

How many GOP retirements are there on the congressional level in Texas?

How we make our polling models robust enough to get the right answer, whether it’s high, low, or in between, is an important one. Accounting for a black swan scenario — a surprise — is always a challenge, in part, because a model that would predict a 1-in-100 outcome is going to be wrong most of the time. But, as we look ahead to the 2020 presidential election and the 2022 midterms, we have to ask ourselves what 2018 and history tell us about how these races might evolve.

The typical mode of modeling turnout is to start from vote history and demography, and then collect observations from voters to account for changes in interest, intent to turnout, and other factors. These models perform really well when turnout holds within a “normal” range for its historical period; they’ve been quite good for the last two decades — for as long as data and technology have allowed them to be built.

But they don’t really account for the kind of epochal changes that defined a 1914, a 1966, a 2004 (to some extent), or now, a 2018 election.

How can we understand the broader social and historical context to try and predict whether 2020 and 2022 will continue the surge in turnout? Will they be like the 2004 election —the first in a series of presidential elections with elevated turnout — or will they be like 1966, a singular surge that quickly gave way to downward trends.

Sorting among several modeling options to find one that will continue to perform well in primaries and “normal” elections, while also capturing a wider range of outcomes (such as 2018) is a major project for the first few months of the year as final voter rosters become available across the country.

But 2018 was a unique event, and those are impossible to predict. The mathematical beauty of a unique event is it can only happen once.