The Repigs know they're vulnerable with regard to the slimy things they've done, the voting machines, the disenfranchisement, the purges, the roadblocks, everything.
So they change the subject to "voter fraud" in an attempt to deflect, confuse, muddle, change the subject and make it seem as though the other side is doing the same thing in different ways and so it's therefore just tit for tat.
Kind of like how the MSM feels they have to "present both sides" even when one side is an outright lie. They're making sure there's another side for the MSM to report, and at the same time making sure they can keep preventing people from registering and voting by making ACORN a "Democratic Dirty Trick".
But that's not good enough for them. Once they've got the evil narrative going (including the outrageously
http://mediamatters.org/items/200410270005">false, fear-incuding statement that ACORN even registered a terrorist in Ohio in 2004), then they have to top it all off by making it not just a Democratic "trick", but an Obama "trick."
http://www.gop.com/obamaacorntree/Note the LARGE print "Barack Obama" right next to the quote, "I've been fighting alongside ACORN..." which makes it appear that it's a direct quote from him (and of course the photo of Obama directly over the quote). Then underneath in small print they say who really said it, calling him "Organizer in chief" which would lead people to believe he might be an organizer for Obama.