Good for him. Bascially, voter caging is when (almost exclusively) the GOP sends out emails to groups who are unlikely to vote for them (Blacks and Hispanics) marked, “Do not forward”, and then they use this to challenge voter rights.
FWIW, the get lots of active duty military doing this.
Not sure how well it will work. Gop is already under a consent decree, as I noted a month ago.