In his paper The Political Economy of Hatred, Ed Glaeser looks at anti-Americanism in the Middle East, anti-Semitism in Europe, and anti-Black hatred in the American South and concludes that hatred is "particularly likely to spread against groups that are politicaly relevant and socially isolated." The social isolation of the object of hatred increases the costs for the in-group to debunk myths, and the political relevance of the group increases the incentives for politicians to target the out-group with hate-creating propaganda.
I think this is a useful model through which to look at McCain's propaganda regarding ACORN, the group he says is now on the verge of maybe perpetrating one of the greatest frauds in voter history in this country, maybe destroying the fabric of democracy." This propaganda has resulted in death threats against ACORN employees and vandalism of ACORN offices. Glaeser's basic theory is that political entrepreneurs who are pro-wealth-redistribution will spread hate-creating stories about rich minorities, while anti-redistribution will spread hate-creaing stories about poor minorities. However it doesn't just have to apply to minorities classified by economics. ACORN and other community organizers are minorities, in that 99% of Americans are not ACORN volunteers or employees, and most don't know ACORN volunteers or employees either.
ACORN, the out-group, is politically relevant both because of their connections to Obama and the Obama campaign, but also because they registered 1.3 million new voters this year.
ACORN is also socially isolated from the target group of McCain's propaganda, not only because there are so few ACORN members in the country, but also because they tend to operate in larger cities, and the target of this propaganda is conservative/GOP voters in suburbs and rural communities (the in-group).
Glaeser's model has four steps:
1) Politicians decide whether or not to broadcast a hate-creating message. My guess is that this occured prior to the GOP national convention, when Giuliani and Palin both devoted chunks of their speeches to ridiculling community organizers. But it could also have happened whenever the campaign realized that they have no shot at winning based on issues, due to the financial/economic situation.
2) In-group members receive the message about the harmfulness of the out-group, and decide whether or not to investigate the truth of this message, and decide whether or not to take action against the out-group. False messages can succeed if in-group members have no incentive to figure out whether the messages are true or not, or if the barriers to finding out the truth are very high. Incentives would be personal, commercial, or other relationships with members of the out-group, which also lower the barriers to the truth. Since ACORN is both socially isolated and not well known by most voters outside of thecurrent voter registration story, incentives are low and barriers are high. While the truth is obviously perfectly available through online news sources, McCain's demographic probably distrusts "liberal media" like ABC (and it doesn't help that CNN bought McCain's propaganda hook, line and sinker).
3) Each group votes for their preferred candidate, and the winner's policies are implemented.
4) The losing group may be harmed by the winning group (the whole point of the propaganda). Here, the ACORN propaganda fits into McCain's larger desperation strategy of associating with people that are "different" from McCain's voters. i.e., if Obama and ACORN steal the election, something bad and vaguely associated with terrorism, socialism, high taxes and black people will happen (all examples are from the central McCain campaign, not the even more explicitlyracist state and local GOP figures).
A few ending notes. First, it's important to recognize the transparently cynical nature of McCain's propaganda campaign against ACORN. This link has a video of McCain congratulating ACORN as "what makes America special" due to their efforts to get immigrants registered to vote.
Second, while McCain rails about "voter fraud" and implies that ACORN is engaged in some conspiracy to steal the election, there is a significant difference between voter fraud and voter REGISTRATION fraud (it's one thing to register Mickey Mouse, it's another thing to try to vote as Mickey Mouse), and the real victim of this voter registration fraud is ACORN itself for being tricked into paying for bogus registrations, which is why they were the ones that reported it to the Feds in the first place. ACORN is legally required in several states to turn in all registration forms, whether they think they are fradulent or not, so as to get around the possibility of organizations throwing out registrations of one party or another. They also noted forms they thought might be fradulent.
Finally, it's important to note that the GOP has a history of crying wolf over voter fraud. The US Attorneys scandal of a couple years ago was partially about Rove firing US Attorneys who were unwilling to prosecute bogus voter fraud cases.