In terms of food, here's a list of favorites. Clam cakes and pizza strips should go over well as party food. Or make some mini hotdogs or mini crescent dogs to dip in homemade New York System Wiener Sauce.
Hillary Clinton was born in Chicago. Here's 20 Chicago drinks to choose from. Green River is the iconic soft drink from IL. If you can't get hold of it, you can make your own limeade.
Slate did a piece on Hillary's favorite food, so we don't have to look far for party ideas. Apparently, what Hillary enjoys most is called an Oliveburger, which is a hamburger topped with pimento-stuffed green olives. So buy some hamburger meat, make some small patties to top with a pimento-stuffed olive and put a toothpick through both. Like with the image to the right, but with an olive on top - bun, lettuce, and tomato optional.
Martin O'Malley is from Maryland. The signature cocktail of Maryland is the Black-Eyed Susan, and the signature soft drink is ginger ale.
Like Rhode Island, Maryland is also known for its crab cakes. Other foods include oysters, chicken with white cream sauce, and Smith Island Cake.
I did a whole post on Bernie Sanders themed drinks, so you can take your pick, but my favorite was this homemade recipe for Vermont Switchel.
Maple is staple in Vermont. There's tons of recipes for maple bread. My personal favorite was this recipe topped with soft cheese. Finish with a toothpick.
Jim Webb is from Missouri. The staple cocktail is the Missouri Mule, and the staple soda is IBC Root Beer.
Finding Missouri staple food was a little difficult, but here's a whole list of food from St. Louis. This includes toasted ravioli, gooey butter cake, and St. Louis style BBQ.