As I described in my 2016 book, The End of White Christian America, something remarkable has happened in the past decade: For the first time in our history, the United States ceased to be a majority white Christian country; white Christians were 54 percent of the population in 2008 but only 47 percent in 2014. Since the book’s publication, those trends have continued unabated. According to data from the Public Religion Research Institute (PRRI), where I am CEO, only 43 percent of the country identified as white and Christian by the 2016 election, and this number drops again to 41 percent in the most recent 2018 data. Notably, the white evangelical Protestant subgroup, the group that threw 80 percent of its votes behind Trump in 2016, has experienced a similar decline. White evangelical Protestants dropped from 21 percent of the population in 2008 down to 17 percent in 2016 and further to 15 percent by 2018, according to PRRI studies.

Niall Ferguson and Eyck Freymann: The coming generation war

These trends seem to fly in the face of the electoral results in 2016. While white Christians composed only 43 percent of the population in 2016, they constituted an estimated 55 percent of voters. And although white evangelical Protestants composed only 17 percent of the public in 2016, they were 26 percent of voters. In other words, in the electorate, white Christians overall were 12 percentage points overrepresented, and white evangelical Protestants were nine percentage points overrepresented.

When white Christians stepped into the voting booth in 2016, their electoral power was comparable to their share of the population back in 2008. The Republican time machine took white evangelicals on an even longer journey. They jumped back to the middle of the George W. Bush era, the last time they made up nearly a quarter of the population.

Read: The last temptation

What fuels the Republicans’ political strength, in other words, is not current white Christian population levels, but the fact that white Christians historically turn out to vote at higher rates than nonwhite and non-Christian Americans. These higher turnout rates are driven by a number of factors. Voting is highly correlated with other forms of civic participation, such as church attendance. Voting is also highly correlated to education levels, and white Christians are more likely than nonwhite Christians to hold a four-year-college degree. Finally, voting is a habit that has been strongly emphasized in white Christian churches, especially among white evangelicals since the rise of the Christian right in the 1980s.

What does all of this mean for 2020? While Republicans will still benefit from the population dynamics of yesteryear, the maximum lag is about two to three presidential-election cycles. According to current projections, 2024 will be the year that white Christians—already less than half the population—will be a minority in the electorate as well. Between now and then, on the one hand, Republicans will need to expand the base of their party if they want to continue to be competitive nationally.

Democrats, on the other hand, need to take seriously the continued strength of this underappreciated Republican asset. Demographic trends may be a bright light on the Democratic Party’s horizon. But unless turnout patterns shift dramatically, next year’s electorate will look more like the America of 2012, not 2020.