From a Bartcop reader(scroll down), this:
Mail-in or absentee ballots require 60 cents postage if mailing from within the continental US. Not a single first-class stamp. It seems there is some difference of opinion between local election officials and the US Postal Service. The election folks say, it should be delivered, even if "postage due", but the USPS says It needs 60 cents postage. I'm not going to take any chances.