From a New York Times story by Vanessa Friedman headlined “Candidates Sell More Then Ideas”:

These days, retail politics has a whole new meaning. At a point in the electoral cycle when candidates are desperate to distinguish themselves and have only minutes onstage to do so, being able to deliver a zinger that will play on via swag is a key advantage.

Ever since the inauguration of George Washington, voters have been participating in the electoral process by means of merchandise. Back then, it was fancy commemorative buttons that were sewn onto clothes (and were, largely, accessible only to the well-off).