Just had to add this: Here's the answer for "may I wear political buttons/clothing to the poll" (I'm paraphrasing):
"In South Carolina, for example, voters are not allowed to wear any campaign paraphernalia, including T-shirts, at the polls. Alabama has no such clothing restrictions, though you can't loiter at the polls or leave any campaign material inside the polling place. In states that forbid campaign wear, officials usually will just ask the voter to remove the hat or button, and either cover up the shirt or turn it inside out. But in San Diego County, they've purchased several dozen paper smocks that voters can use to cover up any political messages. Otherwise, those voters will have to go home and change. It's best to check with your election office for the local rules, or else keep the campaign gear at home."
Somehow, the paper smocks make me laugh! I wonder how many people would really be swayed by the t-shirt on someone in line with them. ("Ooh, nice hair. Oh, look at her t-shirt, she's voting for ___. Hmm, guess I will, too.)