I think GWB's *not* being ISFJ can be clarified further by examining his political platforms:
- Every time Bush has been elected to office (whether as the Texas governor or US President), he's pushed [against a lot of pressure] for squandering the surplus budget on tax cuts. That in itself is very rare for an ISFJ, who are often stereotyped as the frugal pennypincher. Such behavior is irresponsible for an ISFJ. (It is typical, however, for SP types who maximize action/pleasure and don't place as much stock in saving for "rainy days"; they let the future take care of itself.)
- Bush's only real platform in his presidency has been the Iraq War and "searching out the terrorists." ISFJ's would generally NOT persist on sending young Americans overseas to slowly be whittled away for six long years and still refuse to bring people home, regardless of the "national" security. Why? Because they are personal in nature; the plight of the mothers of sons dying in the war would be very very palpable to them and unless they believed the threat was immediate (which it doesn't seem to be), they would eventually not be able to deal with the thought of so many people dying for seemingly needless reasons. Again, ISFJs are very conservative (not "Republican conservative"), just conservative to a fault in the risks they are willing to take. They would be viewing war damages in personal terms rather than large global missions and be much more conservative in their approach. (Again, Bush's behavior is typical SP "Let's do something and sit here on our hands / Throw energy at the problem and we will win!" mentality. He *hates* to sit still, he always has to be *doing* something.)
- Bush's "No Child Left Behind" agenda is not very ISFJ either. It really ignores the plight on individual children and focuses merely on penalizing schools. While ISFJs would see schools as responsible, again the most important thing is the happiness/distress of the individual; poor disadvantaged kids suffering under the system really rings hard on ISFJs' hearts. (It's why Mother Theresa spent her lifeblood on the streets of Calcutta, rather than just sending money or being a politician. It has to be PERSONAL.)
- Bush allowed his political campaign to stoop to nefarious levels during the 2000 primaries and elsewhere. For him, in a political fight, anything goes. (This is more SP.) ISFJ's usually have more integrity; their issues are with another person's integrity, rather than seeking to undermine others. ESFJ might be more apt to promote attacks on others (re: Karen Hughes, one of Bush's campaign advisors at that time). But ISFJ is usually far more soft-spoken and would rather die than stoop to such unpleasantness and purposefully muckraking people in the press.
(Carter was seemingly this way. He refused, as far as I can recall, to be so disparaging just in order to win political battles.)
GWB might seem personable on a folksy level -- connecting with "country/religious folk," but not really where it matters. He's more the person you'd go out with on a Saturday night to raise cain, and not the man you'd expect to tend the farm while you went out to party.
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Also, I feel I must say something about his abysmal early half of his life.
He was the eldest child of 4-5 (?), who constantly was an underachiever and who did the bare minimum to get by. His grades were average at best, and usually in the low end. He scraped by in the military, joining the unit must likely to avoid real duty, and didn't apparently show up as much as he could get away with not showing up. He actively partied and drank until a religious conversion later in life, when he hit bottom.
This doesn't sound very ISFJ either. An ISFJ would typically be ashamed of being so irresponsible and is very much likely to make an actual effort to please parents and meet the standards. They tend to be average (if they are not very smart) up to solid B students (if they work hard), and if they are gifted, they will be A students. But usually not in the bottom unless there's great instability in the home. Again, his behavior earlier in life (before his religious conversion) was much more typical for SP types (especially ESP).