I mean normally the right accuses the left of voter fraud and the left accuses the right of voter suppression, irony would be something like "Chicago officials accuse Justice Department of not looking into claims of the dead voting".

Mind clarifying the source of irony here?

I'd also like to add that Holder deserves this slap in the face after his remarks, voter fraud truly is often very hard to prosecute, since it can be difficult to show criminal intent as opposed to neglect or accident, but denying it happens is like denying jaywalking or illegal Friday night poker games occur because you never bother to prosecute them... though without the moral high ground of being able to say it's not a big deal or worth the resources to look into.