Well, "early and often" is their mantra... Early voting just makes it easier for the same person to show up to the polls more than once with less chance of being noticed.
That's what I was thinking.
When we lived in NY, we signed a book that had our registration number in it. Our signatures were verified to the one's submitted on the voter registrastion form. It was impossible to vote more than once. Today, living in NC, they look you up in a computer data-base, print out your form, and it has to be signed before they activating the touch screen for electronic voting. I doubt that I could get through that process again without a red flag showing I'd already voted.
I guess that can work if you don't use computerized voting. But here in Dallas County, Texas, they scanned my voters' registration card when I was in the first line and checked it against my drivers' license. Printed out something for me to give at the next checkpoint. The next checkpoint chickee checked all that, made me sign and gave me another form to stand in the booth line.