It is said that those that one has discretion over can provide leverage and this can be demonstrated in the way advertising time sellers have bargaining power at holiday time or television shows if their advertisement slots are full. In order for a negotiating side's leverage to work in their favor, the threats or promises they put forth must be perceived as credible by the opposing group. This does not mean that the threats and promises have to be based in facts, but the opposing group must believe that a specific threat or promise can be carried out and that it would make them better or worse off compared to the other side.