I've written quite a bit about how age and generational conflicts are playing an increasingly important role in American politics - but it occurs to me that I've never actually spelled out how this is happening. So I've put together some charts.*
First, it's worth revisiting a few polls that reveal age inflections in our political polarization:
On basically every major political question you can name, young voters are more progressive than older voters. Young voters overwhelmingly prefer Sanders to Clinton, Clinton to Trump, and Socialism to Capitalism; older voters hold the exact opposite views.
This already is a recipe for generational conflict - but on top of polarized political preferences, we are also seeing massive changes in the sizes of different generational cohorts:
By 2040 Boomers will no longer be the largest generation, and by 2046 Millennials will have assumed that role for the foreseeable future. By 2053 there will be two Millennials for every Boomer.
Of course, age-inflected political polarization and changing population sizes will only impact things like electoral outcomes insofar as anyone bothers to vote. And while this may seem like bad news for Millennials, who vote at lower rates than everyone else, voting patterns tend to change with age. As the Millennial cohort grows older, they're likely to vote more frequently. If we assume that everyone's voting habits as they grow older will tend to match the age equivalent rates of 2016, future turnout will probably look something like this:
Here, superior turnout only buys Boomers an extra year on top - they lose their electoral plurality in 1941. Millennials gain the plurality a decade later, and by 2060 they outvote every other group combined.
Suppose, then, that these political preference and turnout trends all hold for future Democratic primaries - and suppose that for the next few decades, we continue to see primaries pitting Clinton-type candidates against Sanders-type candidates. Cross reference the above trends, and this is what our future politics would look like:
What this chart tells us is that by 2039, among Americans who are currently eligible voters, support for Sanders-type candidates will completely overwhelm support for Clinton-type candidates. This model relies on some awfully big assumptions, but most of them - population growth projections and lifetime political preference retention - are grounded in fairly rigorous science.
The most significant unknown here is whether or not Sanders-and-Clinton-style candidates continue to run in the primaries. Another crucial consideration here is that by 2039, in addition to the voters considered here, at least 90 million Americans who are currently under 18 (or are not born yet) will have become eligible voters. We can't predict this age cohort's preferences with any certainty, but if the trend of younger voters being progressive voters holds, Sanders-style candidates would be winning well before 2039.
What we can be sure of, regardless, is that the age of the Boomers is coming to an end. Their generation is rapidly shrinking, and no amount of superior turnout will save them in the long-run. I think it fairly safe to assume that they'll resent this diminished influence after a good half century of political hegemony, and that they'll leverage all of the entrenched institutional and systematic privileges and advantages that they've built for themselves over the years in order to try to retain their power. That strategy can't last forever either, however, and as the rude teen barbarians crash against the gates of old privilege, it's gonna get ugly.
* Brief note on terminology: due to constraints on available data, I've divided the population into four age brackets - 18-29, 30-44, 45-64, and 65+. These brackets correspond roughly, but not exactly, to the commonly accepted "generational" divisions (between Millennials and Gen-X, Gen-X and Boomers, and Boomers and the Silent Generation). These divisions are completely arbitrary and artificial, but the difference explains why, for example, some analysts already consider Boomers a minority generation. For the sake of this analysis this difference isn't particularly important.