Looks like the existing Eldorado Resorts Casinos are transitioning to a common One Club card, not to be confused with the older One Club cards used by MGM Resorts then Mandalay Bay and just Circus Circus Reno.

Here's a link with info on the new cards although it's just listed under Scioto Downs currently
http://www.sciotodowns.com/gaming/join-one-club