WILLIAMSON COUNTY, TENNESSEE — Kristen Grimm has just realized she forgot to clean out her minivan. She gushes her apologies as she pulls open the driver’s side door, revealing a passenger seat littered with palm cards and newspapers. Her backseat, filled with yard signs, an extra coat, and a change of shoes is also not rider-ready.
But her dismay about the messy car doesn’t — or rather, it can’t — last long before she’s on to the next thing: A phone call from a fr...