One of the reasons that Democratic whining and fear-mongering about disenfranchisement is so much more effective that Republican worries about vote fraud is that the victim in one case is clear, while both the victim and perpetrator in the other are hard to identify.
In order to commit disenfranchisement, really commit disenfranchisement, some specific individual needs to be refused his ability to vote. That individual can be identified, and held up as a specific victim. More importantly, those "pre-emptive strikes" can be effective, because even if the presumed victim is a class, or hypothetical, any one of us can imagine ourselves as being turned away, and how outraged we would be. Bill Johnson apparently has retained an entire army of attorneys based on just such a fantasy.
The flip-side is much harder for most of us to personalize. In an election with millions of voters, we see the damage from one fraudulent vote as being, in some sense, distributed among the entire voting population. If that fraudulent vote is for Kerry, then sure, some Bush voter has had his vote canceled out, but which one? Surely not all of us, and surely not any one in particular. At the same time, the very nature of vote fraud conceals the perpetrator, since he needs to either invent a non-existant identity, or steal someone else's, in order to commit his crime. The inability to identify either the victim or the criminal is one of the reasons that vote fraud has received so little attention compared to intimidation or disenfranchisement.
This asymmetry extends to other areas of public policy. I can point to specific jobs lost to competition; I can't point to specific jobs created by free trade. It was only when those opposed to minority set-asides and racial quotas were able to produce specfic victims that they were able to start winning a few court decisions. Environmentalists have the hardest time imposing regulation where specific ecnomic victims can be found, but all too often the costs of regulation are distributed across an entire inustry or economic sector.
Fingerprinting and photo-taking are illegal at the polls. Some of the ID required barely qualifies as ID at all. Election judges will need astounding memories to recognize the faces of people foolish enough to try to vote twice in the same precinct. While someone, some individual being turned away, has immediate sympathy and an immediate complaint. The only way to redress this asymmetry in the public mind is to relentlessly push the issue.