The "coattail" effect works best when there is a synergy between the two candidates. And an alliance between James Webb and Phil Kellam would optimize the effect for both - getting voters out who would be enthusiastic for both candidates.
Kellam is in a military-heavy Second District - Norfolk, Virginia Beach, etc. Webb is a former Navy Secretary who would likely appeal to the enlisted in the Second. Webb's coattails will draw out these voters to pull the Democratic lever. And down ticket they will find Kellam, an already popular local figure who is running on results, creating an enticing Democratic slate for the voters in the Second District.
A Kellam-Webb alliance would be a powerful combination ... and a career-ending problem for George Allen and Thelma Drake.