McCain's selection of Sarah Palin as his running mate was a naked play to garner the support of the so-called Republican base - narrow fundamentalist Christians. Let me be clear that NOT all Fundamentalist Christians (and not even the majority of them) are "radical" (meaning wanting to take over the government of the United States and reshape the country into a religious fiefdom). However, that is the base that McCain went after. It is the "base" that George Bush supposedly captured.
Starting with the meme that Obama was a Muslim schooled in madrassas, the seed was planted that he was a "born and trained" terrorist. Even the long term relationship with Reverend Wright was not portrayed as proof of his Christianity, but was "proof" of his hatred of the United States. (Regardless that it should make no difference even if Obama was Muslim.) Repeatedly, McCain and - as a drum beat - Palin, have told the groups they are speaking to that they are "scared" of Obama. More recently, it has been the constant meme that Obama consorts with "terrorists" - namely Bill Ayres who was a leader of the Weatherman Underground 40 years ago.
As the carefully crafted memes aimed at inspiring fear of Obama in relationship to race, terrorism, and anti-Americanism, have been accelerated, the crowds at McCain-Palin political rallies have seemed more of a mob than a political rally. The more vehement the rhetoric, the more attractive McCain and Palin have become to the racist "right." It was predictable. It was intentional. It has not stopped.
Here is a CNN report on Palin accusing Obama of "palling around with terrorists."
Here is video from a McCain rally where the carefully instilled memes are repeated back from the crowd - clearly a political "success" for the McCain campaign.
Which has brought McCain to the point of defending Obama's character.
Of course, underlying all of this is the issue of race. The McCain campaign doesn't even need to play the "race card" because it is embedded in the "American" consciousness. They just need to hint and it comes to the surface. This is obvious in crowd comments using racial epithets and saying that terrorism is "in his blood line."