Growing evidence suggests that George W. Bush abruptly left his Texas Air National Guard unit in 1972 for substantive reasons pertaining to his inability to continue piloting a fighter jet.

A months-long investigation, which includes examination of hundreds of government-released documents, interviews with former Guard members and officials, military experts and Bush associates, points toward the conclusion that Bush’s personal behavior was causing alarm among his superior officers and would ultimately lead to his fleeing the state to avoid a physical exam he might have had difficulty passing. His failure to complete a physical exam became the official reason for his subsequent suspension from flying status.

This central issue, whether Bush did or did not complete his duty–and if not, why–has in recent days been obscured by a raging sideshow: a debate over the accuracy of documents aired on CBS’s 60 Minutes. Last week CBS News reported on newly unearthed memos purportedly prepared by Bush’s now-deceased commanding officer. In those documents, the officer, Lieut. Col. Jerry Killian, appeared to be establishing for the record events occurring at the time Bush abruptly left his Texas Air National Guard unit in May 1972. Among these: that Bush had failed to meet unspecified Guard standards and refused a direct order to take a physical exam, and that pressure was being applied on Killian and his superiors to whitewash whatever troubling circumstances Bush was in.

Questions have been raised about the authenticity of those memos, but the criticism of them appears at this time speculative and inconclusive, while their substance is consistent with a growing body of documentation and analysis.

If it is demonstrated that profound behavioral problems marred Bush’s wartime performance and even cut short his service, it could seriously challenge Bush’s essential appeal as a military steward and guardian of societal values. It could also explain the incomplete, contradictory and shifting explanations provided by the Bush camp for the President’s striking invisibility from the military during the final two years of his six-year military obligation. And it would explain the savagery and rapidity of the attack on the CBS documents.

In 1972 Bush’s unit activities underwent a change that could point to a degradation of his ability to fly a fighter jet. Last week, in response to a lawsuit, the White House released to the Associated Press Bush’s flight logs, which show that he abruptly shifted his emphasis in February and March 1972 from his assigned F-102A fighter jet to a two-seat T-33 training jet, from which he had graduated several years earlier, and was put back onto a flight simulator. The logs also show that on two occasions he required multiple attempts to land a one-seat fighter and a fighter simulator. This after Bush had already logged more than 200 hours in the one-seat F-102A.

Military experts say that his new, apparently downgraded and accompanied training mode, which included Bush’s sometimes moving into the co-pilot’s seat, can, in theory, be explained a variety of ways. He could, for example, have been training for a new position that might involve carrying student pilots. But the reality is that Bush himself has never mentioned this chapter in his life, nor has he provided a credible explanation. In addition, Bush’s highly detailed Officer Effectiveness Reports make no mention of this rather dramatic change.

A White House spokesman explained to AP that the heavy training in this more elementary capacity came at a time when Bush was trying to generate more hours in anticipation of a six-month leave to work on a political campaign. But, in fact, this scenario is implausible. For one thing, Guard regulations did not permit him to log additional hours in that manner as a substitute for missing six months of duty later on. As significantly, there is no sign that Bush even considered going to work on that campaign until shortly before he departed–nor that campaign officials had any inkling at all that Bush might join them in several months’ time.

Bush told his commanding officers that he was going to Alabama for an opportunity with a political campaign. (His Texas Air National Guard supervisors–presumably relying on what Bush told them–would write in a report the following year, “A civilian occupation made it necessary for him to move to Montgomery, Alabama.”) But the timing of Bush’s decision to leave and his departure–about the same time that he failed to take a mandatory annual physical exam–indicate that the two may have been related.

Campaign staff members say they knew nothing of Bush’s interest in participating until days before he arrived in Montgomery. Indeed, not one of numerous Bush friends from those days even recalls Bush talking about going to Alabama at any point before he took off.

Bush’s behavior in Alabama suggests that he viewed Alabama not as an important career opportunity but as a kind of necessary evil.

Although his role in the campaign has been represented as substantial (in some newspaper accounts, he has been described as the assistant campaign manager), numerous campaign staffers say Bush’s role was negligible, low level and that he routinely arrived at the campaign offices in the afternoon hours, bragging of drinking feats from the night before.

According to friends of his, he kept his Houston apartment during this period and, based on their recollections, may have been coming back into town repeatedly during the time he was supposedly working full-time on the Alabama campaign. Absences from the campaign have been explained as due to his responsibilities to travel to the further reaches of Alabama, but several staffers told me that organizing those counties was not Bush’s de facto responsibility.

Even more significantly, in a July interview, Linda Allison, the widow of Jimmy Allison, the Alabama campaign manager and a close friend of Bush’s father, revealed to me for the first time that Bush had come to Alabama not because the job had appeal or because his presence was required but because he needed to get out of Texas. “Well, you have to know Georgie,” Allison said. “He really was a totally irresponsible person. Big George [George H.W. Bush] called Jimmy, and said, he’s killing us in Houston, take him down there and let him work on that campaign…. The tenor of that was, Georgie is in and out of trouble seven days a week down here, and would you take him up there with you.”

Allison said that the younger Bush’s drinking problem was apparent. She also said that her husband, a circumspect man who did not gossip and held his cards closely, indicated to her that some use of drugs was involved. “I had the impression that he knew that Georgie was using pot, certainly, and perhaps cocaine,” she said.

Now-prominent, established Texas figures in the military, arts, business and political worlds, some of them Republicans and Bush supporters, talk about Bush’s alleged use of marijuana and cocaine based on what they say they have heard from trusted friends. One middle-aged woman whose general veracity could be confirmed told me that she met Bush in 1968 at Hemisfair 68, a fair in San Antonio, at which he tried to pick her up and offered her a white powder he was inhaling. She was then a teenager; Bush would have just graduated from Yale and have been starting the National Guard then. “He was getting really aggressive with me,” she said. “I told him I’d call a policeman, and he laughed, and asked who would believe me.” (Although cocaine was not a widespread phenomenon until the 1970s, US authorities were struggling more than a decade earlier to stanch the flow from Latin America; in 1967 border seizures amounted to twenty-six pounds.)

Bush himself has publicly admitted to being somewhat wild in his younger years, without offering any details. He has not explicitly denied charges of drug use; generally he has hedged. He has said that he could have passed the same security screening his father underwent upon his inauguration in 1989, which certifies no illegal drug use during the fifteen preceding years. In other words, George W. Bush seemed to be saying that if he had used drugs, that was before 1974 or during the period in which he left his Guard unit.

The family that rented Bush a house in Montgomery, Alabama, during that period told me that Bush did extensive, inexplicable damage to their property, including smashing a chandelier, and that they unsuccessfully billed him twice for the damage–which amounted to approximately $900, a considerable sum in 1972. Two unconnected close friends and acquaintances of a well-known Montgomery socialite, now deceased, told me that the socialite in question told them that he and Bush had been partying that evening at the Montgomery Country Club, combining drinking with use of illicit drugs, and that Bush, complaining about the brightness, had climbed on a table and smashed the chandelier when the duo stopped at his home briefly so Bush could change clothes before they headed out again.

It is notable that in 1972, the military was in the process of introducing widespread drug testing as part of the annual physical exams that pilots would undergo.

For years, military buffs and retired officers have speculated about the real reasons that Bush left his unit two years before his flying obligation was up. Bush and his staff have muddied the issue by not providing a clear, comprehensive and consistent explanation of his departure from the unit. And, peculiarly, the President has not made himself available to describe in detail what did take place at that time. Instead, the White House has adopted a policy of offering obscure explanations by officials who clearly do not know the specifics of what went on, and the periodic release of large numbers of confusing or inconclusive documents–particularly at the start of weekends and holiday periods, when attention is elsewhere.

In addition, the Bush camp has offered over the past few years a shifting panoply of explanations that subsequently failed to pass muster. One was that Bush had stopped flying his F-102A jet because it was being phased out (the plane continued to be used for at least another year). Another explanation was that he failed to take his physical exam in 1972 because his family doctor was unavailable. (Guard regulations require that physicals be conducted by doctors on the base, and would have been easily arranged either on a base in Texas or, after he left the state, in Alabama.)

One of the difficulties in getting to the truth about what really took place during this period is the frequently expressed fear of retribution from the Bush organization. Many sources refuse to speak on the record, or even to have their knowledge communicated publicly in any way. One source who did publicly evince doubts about Bush’s activities in 1972 was Dean Roome, who flew formations often with Bush and was his roommate for a time. “You wonder if you know who George Bush is,” Roome told USA Today in a little-appreciated interview back in 2002. “I think he digressed after awhile,” he said. “In the first half, he was gung-ho. Where George failed was to fulfill his obligation as a pilot. It was an irrational time in his life.” Yet in subsequent years, Roome has revised his comments to a firm insistence that nothing out of the ordinary took place at that time, and after one interview he e-mailed me material raising questions about John Kerry’s military career. Roome, who operates a curio shop in a Texas hamlet, told me that Bush aides, including communications adviser Karen Hughes, and even the President himself stay in touch with him.

Several Bush associates from that period say that the Bush camp has argued strenuously about the importance of sources backing the President up on his military service, citing patriotism, personal loyalty and even the claim that he lacks friends in Washington and must count on those from early in his life.

In 1971 Bush took his annual physical exam in May. It’s reasonable to conclude that he would also take his 1972 physical in the same month. Yet according to official Guard documents, Bush “cleared the base” on May 15 without doing so. Fellow Guard members uniformly agree that Bush should and could have easily taken the exam with unit doctors at Ellington Air Force Base before leaving town. (It is interesting to note that if the Killian memos released by CBS do hold up, one of them, dated May 4, 1972, orders Bush to report for his physical by May 14–one day before he took off.)

Bush has indicated that he departed from Ellington Air Force Base and his Guard unit because he had been offered an important employment opportunity with a political campaign in Alabama. The overwhelming evidence suggests, however, that the Alabama campaign was a convenient excuse for Bush to rapidly exit stage left from a Guard unit that found him and his behavior a growing problem. If that’s not the case, now would be an excellent time for a President famed for his superlative memory to sit down and explain what really happened in that period.