LGF reports another issue. 19 May 1972 mentions that Bush is working on a campaign at that time. There is no record of such a campaign in Bush's biography.
http://littlegreenfootballs.com/weblog/?entry=12555_CBS_Docs-_Bush_Working_on_Nonexistent_Campaign
Study later Bump
Found this in the replies for your link and at another site I was just on:
The campaign was not for George HW Bush, it was for Republican Winton Blount, who was running for the senate in Alabama.