If old people really do swing to Biden, 2020 will be an interesting coalition of the very young and very old voters uniting behind Biden for very different reasons.
Thats how things were in the New Deal Era with the Democrats getting big numbers with Young and Old Voters while Middle-Aged voters were a Republican Leaning Group.
Also remember Bush's best group were people aged 30-49(which is how the exit poll did it then) while Trump's is 45-64 so basically the core Republican group has been for decades the people who came to age under Reagan
https://ropercenter.cornell.edu/how-groups-voted-2004
