For first time, millennials and Gen-X were a majority of electorate in 2016

Political strategists, take note: for the first time, Millennials and Gen-Xers outvoted their elders in 2016, according to data from the Pew Research Center.

Fully 69.6 million Millennials (defined as people who were 18 to 35 in 2016) and members of Generation X (ages 36 to 51) cast votes in 2016, according to a Pew analysis of data from the Census Bureau. By comparison, 67.9 million Boomers and members of older generations voted.

This is the culmination of a steady march of the young electorate slowly catching up to the middle-aged and elderly electorates in terms of size.

It's not exactly surprising news — more and more Millennials have been hitting voting age all the time, while Boomers and older Americans are dying off.

But it is nevertheless an important reminder to parties and politicians that a shifting electorate could mean shifting strategies for future campaigns.

For now, the growing number of younger voters may seem like a problem for Republicans. Younger voters are significantly more likely to identify as Democratic than older cohorts, according to 2016 data from Pew. That year, 55 percent of Millennials identified as Democratic or leaned Democratic. That share dropped off in each successive older generation — and the share of Republicans grew in each successive generation.

But then, there could be a bright spot or two for conservatives. For example, a 2016 study found that at high school graduation, Millennials (defined in this study as being born between 1980 and 1994, so this wouldn't include 2016's youngest voters) were more likely to identify as conservative than Generation X or Boomers were at the same age.

If anything, Millennials may be more polarized than their parents and older siblings were when they were young. "Fewer 12th graders and entering college students identified as moderates in the 2010s compared to the late 1970s and 1980s and more identified as radical, very liberal, or very conservative," researchers wrote in that 2016 paper.

That kind of polarization may only intensify in coming years. In a blog post today at Demos, a left-leaning think tank, Sean McElwee points out that young Democratic primary voters and donors are both more liberal than other democrats their age and more liberal than older primary voters and donors. All of that means that the Democratic party will soon be pulled further left, McElwee predicts.

That liberalism was on display in 2016, when young voters in particular responded strongly to Bernie Sanders' socialist message. Indeed, some 2016 polls showed that millennials were more likely than older voters to view socialism favorably.

Political ideologies aside, a few other Millennial traits will indubitably shape future politics.

For one thing, they're more diverse, according to a 2016 Brookings analysis — in particular, the younger the generation, the less white it is and the more Hispanic it is.

Millennials are also less religious than their elders, meaning that candidates who make their faith central to their political campaigns (think Ted Cruz and Mike Huckabee) might find winning votes increasingly difficult in the future.

But longer-term, the question is how young voters' political preferences will change as they age. Conventional wisdom says that voters grow more conservative as they get older, and there is some evidence to back this up — by some polling, Gen X and Baby Boomer voters became less supportive of bigger government as they aged. But it's not clear to what degree the idea of conservatism growing with age is true — indeed, some recent research has called that into question on social issues in particular.

Not only that, but research has shown that events in Americans' early voting years tend to affect them for the rest of their voting lives (though this is more true for white than minority voters, according to a 2014 paper). If that's true, a deeply unpopular President Trump — particularly among today's young voters — might have lasting, negative reverberations for future Republicans.

One other major question for how Millennials shape future elections is whether they increase their voting rates. Perhaps the most striking thing about Pew's new finding that it didn't come sooner. In 2016, there were far more eligible young voters — 126 million in Gen X and Millennials — than older voters, with nearly 108 million eligible between the Boomer and Silent generations.

But younger voters have only just now overtaken their elders because younger generations — and especially Millennials — have lower voting rates than older generations, Pew also found. Only around half of Millennials voted in 2016, compared to around two-thirds of older cohorts.