One of the most durable forces shaping the U.S. electorate is that voters tend to lean more Republican as they age.

But it also matters where they begin on the political spectrum, and there are indications that millennials and the oldest members of Generation Z started out more liberal than prior generations. That has made them a crucial base of support for Democrats, even as some other groups of voters have moved away from the party.

Gen Z entered the voting pool just as Donald Trump took office and the U.S. was upended by the Covid-19 pandemic. Most of its members are too young to vote. Early data suggest the group is strongly Democratic in part because young people favor liberal stances on social issues, particularly LGBTQ rights.

Gaining assets and income pushes voters toward conservative fiscal policies, such as lower taxes, that allow them to keep more of their money, researchers say. As Americans move from midlife to retirement, they are more likely to favor stability over change, and less likely to back liberal policies that upset the social order.

This rightward shift is likely to affect who wins elections in 2024 and the years beyond. One in six Americans is age 65 or over, up from one in eight a decade prior, according to the most recent decennial census. A slump in births that started in 2008 will eventually give way to a smaller pool of new, young voters.

On its face, the shift bodes well for Republicans. Yet its effects have been muted by the size and liberal bent of millennials now approaching middle age, and the more solidly blue partisanship of Gen Z voters just entering the electorate.