“Chum” is campaign gear such as bumper stickers, lawn signs, and campaign buttons.
The term is derived from the bait used to catch fish because in a political campaign these items are frequently used to entice volunteers and voters to get more involved in a campaign or bringing them to events. The distribution of chum is organized by a candidate’s advance man.
Time notes that during the 2008 presidential campaign, Barack Obama’s campaign “set up little tabletop trinket shops, known as ‘chum stores’ because all those little Obama-branded doodads aren’t only keepsakes; they are also bait. Every person who buys a button or hat is recorded as a campaign donor. But the real goal of the chum operations was building a list of workers, supporters and their e-mail addresses.”