There are three inducements of support that Americans are powerless against: the promise of whiter teeth, the suggestion of no-diet weight loss and the cause of justice.
Political campaigns tend to couch their appeals in terms of the last, though parts of the Romney-Ryan economic pitch could be described as the second. In today's truly divisive debates, both parties have usually engineered a rhetorical claim to the side of fairness: gay rights advocates propelled themselves forward when they began to argue for "marriage equality" against the outdated complaint of "special rights".
Americans rankle at unearned privileges as much as they rally, in the main, to equality. Hence the widespread, enthusiastic support of voter ID laws (theypoll with about 75% in favor) makes total sense if you see the laws exactly the way their authors and promoters talk about them – as barriers to voter fraud. After all, voter fraud is when criminals unfairly manipulate voting, the most basic expression of fairness available in a democracy.
There are no witnesses to these purges, no ugly footage to brandish on the evening news. What's more, there is not an equal and opposing force: no computer program that can create a list of people who should be allowed to vote. The Common Cause/Demos paper last week that spurred some the current coverage of voter ID makes suggestions for leveling the playing field, such as making challenges to voter registration as individuated as possible (requiring a signed affidavit for each challenge, for instance).
In the end, though, once challenged, the only way for a would-be voter to push back is by a literal act of personal integrity: showing up at the county registrar's office or hearing, usually. While I can imagine the satisfaction of telling a conservative activist who has challenged my rights to "say that to my face", the fact is that if someone has been challenged because he or she has no driver's license or is struggling with permanent housing, they may not even find out they've been challenged.