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.
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.”