As Sen. Joni Ernst walked around the Big Barn Harley-Davidson in Des Moines Saturday, shaking hands and taking photos with constituents, she insisted that the day’s events were something other than political.

“We don’t really talk politics so much when we’re on the motorcycle,” the Iowa Republican said. “It’s more a symbol of freedom and being out on the road and experiencing life on the road.”

Ernst and her guests, a group of more than 400 bikers, would soon hit the road for her the second annual Roast and Ride, an event that officially designed to honor veterans and unofficially designed to serve as a cattle-call for presidential candidates in a battleground state. Last year’s event attracted Marco Rubio, Rick Perry, Ben Carson and Carly Fiorina among others, while Donald Trump headlined this year’s event.

But even if the speakers hadn’t made it clear that the Roast and Ride is a conservative event, the motorcycles themselves would have done the trick. In recent years, Republicans have come to adopt the motorcycle—and Harley-Davidsons, especially—as a symbol of conservatism, a metaphor for the freedom and individualism they hold sacrosanct.

Apart from Ernst, motorcycle-riding Republican politicians include Wisconsin Gov. Scott Walker, Illinois Gov. Bruce Rauner, former California Gov. Arnold Schwarzenegger, former Utah Gov. Jon Huntsman, former Wisconsin Gov. Tommy Thompson and former Indiana Gov. Mitch Daniels. (Some Democrats also ride: West Virginia Sen. Joe Manchin, New York Gov. Andrew Cuomo and former Montana Sen. Max Baucus.)

Among Republican politicians, the Milwaukee-based Harley-Davidson is the preferred ride.

“There’s a particular made-in-America brand that is the Harley-Davidson that right-wing Republicans sort of gravitate toward,” said Suzanne Ferriss, professor emeritus at Nova Southeastern University who has researched motorcycle culture.

Read more at: Time