I'll let you in on a secret, and since I'm indigenious here I know whereof I speak: Bush did know, beforehand, this audience would be staunchly supportive. First of all patriotism, and support for the troops, is unchallenged here. Secondly, this area is a collection of small communities and the locals have unwritten rules to keep the peace: Democrats (who are strong here, thanks to the unions) don't disrupt GOP events and vice versa. These locals also are mostly steel workers or real country folk, they've lived on the river valley for generations and they're tough and direct...even the Democrats genuinely support our troops. Thirdly, Bush has been here before (and his audiences then were hand-picked...sort of, just to keep out pre-election rabble, but I saw well-known Democrats at these events.) Fourthly, all the above was well-known by Bush, et al.
The point I want to make is that this time, when Bush is allegedly in "trouble," there was no effort to pre-select the audience. There simply was no need.
PS: I worked for the Bush campaign and even have a genuine gold-embosssed letter from the Pres. hisself, suitable for framing, and even I didn't get advance notice or a personal invite to the event in Wheeling.