The Pew Study of non-voter demographics is from 2010, but I suspect that not that much has changed on that score in the past decade.
None of this is terribly surprising. But, it does help quantify the electoral impact of low voter turnout in the United States.
Later in the report, it notes that non-voters are somewhat more liberal than voters which goes hand in hand with being less Republican than the general public.
Turnout will continue to be a pivotal issue in the 2020 election.