A facility for adjusting the execution of an advertising campaign in which advertising messages are presented using a plurality of advertising alternatives as described. During a first time period, the facility presents advertising messages using each of the advertising alternatives in accordance with an initial allocation for each of the advertising alternatives. Also during the first time period, the facility tracks the performance of the advertising campaign with respect to each of the advertising alternatives. Based upon the tracking during the first time period, the facility attributes a performance score to each of the advertising alternatives for the first time period. The facility compares these scores, and, based upon the comparison, adjusts the allocations for the advertising alternatives so as to increase one or more allocations for advertising alternatives which compare favorably in the comparison, and so as to reduce one or more allocations for advertising alternatives comparing disfavorably in the comparison. The facility then, during a second time period, presents advertising messages using each of the advertising alternatives in accordance with the adjusted allocation for each of the advertising alternatives.