When did Bush begin losing support? 2005, after Hurricane Katrina, and when the Iraq war began to hit small town America hard, when everyone knew someone who had lost a son or daughter in Iraq. And then when the economic slowdown of 2006 hit, they began to flip on the GOP.
Well, Bush really started losing support a few days after 9/11. It was just that 9/11 was such an enormous bounce for him that he could afford to bleed support and still win in '04. And for the record, Trump's approval right now is pretty comparable to Bush's after Hurricane Katrina.