11. A method of selecting content items based on prior interactions with information resources, comprising: identifying, by a data processing system having one or more processors, a first plurality of content items based on a first match between a query and a keyword associated with the first plurality of content items, the query received subsequent to a client device performing a pre-specified interaction; identifying, by the data processing system, a second plurality of content items based on the first match and on a second match between an account identifier associated with the client device and a retargeting identifier of a retargeting set, the retargeting identifier included into the retargeting set responsive to the client device performing the pre-specified interaction; selecting, by the data processing system, from the first plurality of content items and the second plurality of content items, a content item based on selection criteria associated with each of the first plurality of content items and with each of the second plurality of content items, the second plurality of content items including the content item; and providing, by the data processing system, to the client device, the content item to present on an information resource.
11. A method of selecting content items based on prior interactions with information resources, comprising: identifying, by a data processing system having one or more processors, a first plurality of content items based on a first match between a query and a keyword associated with the first plurality of content items, the query received subsequent to a client device performing a pre-specified interaction; identifying, by the data processing system, a second plurality of content items based on the first match and on a second match between an account identifier associated with the client device and a retargeting identifier of a retargeting set, the retargeting identifier included into the retargeting set responsive to the client device performing the pre-specified interaction; selecting, by the data processing system, from the first plurality of content items and the second plurality of content items, a content item based on selection criteria associated with each of the first plurality of content items and with each of the second plurality of content items, the second plurality of content items including the content item; and providing, by the data processing system, to the client device, the content item to present on an information resource. 17. The method of claim 11 , comprising: identifying, by the data processing system, the second plurality of content items based on the first match, the second match, and a third match between the query and a targeting keyword associated with the second plurality of content items.