A running connection
When shopping at Jewel-Osco, I don't pay much attention to the loudspeaker playing music and making fund-raising appeals.
Last night, however, a promotion for a race caught my ear, because the description included the phrase, "...a CARA-Registered race..."
That was unusual. Most race announcements simply address the cause, assuming that will engage listeners. This one, additionally, boasted of the quality of the race by mentioning its connection to a running organization.
Most runners participate in races to run, not to support a cause. When your event has a relationship with a running club or association, a running publication, or anything dealing with running, include it in your ads, PSAs, and other public announcements.
Runners can donate to your cause without showing up. If you want them to participate in the event, tout the quality of the race - that's what will grab them.