Courtesy of the 5 Minute Movie Guide:
When Mary Mapes a senior Producer at CBS who was responsible for the prestigious 60 Minutes TV Program led by veteran newsman Dan Rather, got wind of a potential story about Bush managing to avoid even his easy stint with the Guard, she started a whole investigation. With the approval of the Network's bosses, and encouraged by Rather, she got together a small very experienced team to check out documents purportedly from the files of Bush's commanding officer, the late Lieutenant Colonel Jerry B Killian that confirmed that Bush had been been AWOL for most of his alleged military service. Mapes had learned that the then-Texas Lieutenant Governor Ben Barnes had admitted making phone calls to get Bush into the Guard, as he claimed to have done for the children of several other influential Texans. The story was that Bush had received preferential treatment in passing over hundreds of applicants to enlist in the Texas Air National Guard in order to avoid being drafted and sent to fight in Vietnam after he had graduated from Yale in 1968.
When the 60 Minute team had gathered substantial evidence supporting the claims their aired their findings in a special edition of their show, but before Rather and Mapes could even celebrate their major news coup, they were immediately subject to some to some very virulent criticism. It all focused on the actual authenticity of the documents that they had received from Bill Burkett, who was a retired Lt. Colonel with the Guard. Suddenly there was a very aggressive and effective campaign mounted to discredit the entire 60 Minute Team by some very influential and important political figures simply by rubbishing the validity of the evidence. It eventually resulted in Rather prematurely ending his distinguished career in disgrace and ignominy, and Mapes and her entire team being fired.
One of the things that I find fascinating about this whole episode was the revelation that Mary Maples had been in possession of this story back in 2000, BEFORE George W. was ever elected President, and did not pursue it due to the death of her mother.
Just imagine how different the world might have been if this story had come out before Bush was President, and had so many tools to suppress damaging stories at his disposal.
If you are looking for deep background on the allegations made about W's National Guard service, and the aggressive attacks that were launched to discredit Dan Rather and his team, you can visit Who, What, Why and read more about it here and here.
For the record I watched this whole thing unfold and have ALWAYS believed that Dan Rather was completely right in his reporting, and that what happened to him was one of the most shameful things to happen in American journalism.