] On May 26, 1972, Bush asked in writing for reassignment
] to an Air Reserve squadron in Alabama so he could work on
] the U.S. Senate campaign of Republican Winton
] "Red" Blount, a close friend of his influential
] father. That was rejected because Bush was obligated to
] serve as a Ready Reservist until May 26, 1974, and was
] ineligible for assignment to the Air Reserve. About three
] months later, on Sept. 5, Bush asked to perform
] "equivalent duty" with the Alabama unit from
] September to November. Killian approved the request a day
] later. The orders went through on Sept. 15, and while
] Bush had missed the Sept. 9-10 unit training assembly,
] the document noted he could make the next two.
] Bush's Officer Military Record shows an Oct. 1,
] 1973, discharge from the Texas Air National Guard and
] transfer to the Alabama unit.

I like this article because it seems to have a more balanced view of what's known about the situation, and because it seems to be written from a military perspective rather than a political one.

Air Force Times: Bush and the Guard